Java crypto

java crypto

Java Cryptography Architecture — это криптографический фреймворк, входящий в состав платформы Java. JCA предоставляет API для различных целей, в том числе шифрования, управления ключами, генерации криптографически стойких псевдослучайных чисел и. myusinsk.ruRandom. • myusinsk.ru • myusinsk.rueDigest. • myusinsk.ru • myusinsk.ruure. @since Провайдер Java CSP RSA (требует установки компонента провайдера КриптоПро CSP с реализацией иностранных алгоритмов: Crypto-Pro Enhanced RSA and AES CSP).

Java crypto

Cipher представляет криптографический метод. Шифр может употребляться как для шифрования, так и для расшифровки данных. Класс Cipher разъясняется наиболее тщательно в последующих разделах, ниже будет его короткое описание. Создание экземпляра класса шифр, который употребляет метод шифрования AES для внутреннего использования:. Способ Cipher. В приведенном выше примере:.

Перед внедрением экземпляра шифра его нужно инициализировать. Экземпляр шифра инициализируется вызывом способа init. Способ init воспринимает два параметра:. 1-ый параметр показывает, режим работы экземпляра шифр: шифровать либо расшифровывать данные. 2-ой параметр показывает, какой ключ они употребляют для шифрования либо расшифровки данных. Обратите внимание, что метод сотворения ключа в этом примере опасен и не должен употребляться на практике.

В данной статье в последующих разделах будет поведано, как создавать ключи наиболее безопасно. Чтоб инициализировать экземпляр шифра для расшифровки данных, вы должны применять Cipher. Опосля инициализации шифра вы сможете начать шифрование либо расшифровку данных вызовом способов update либо doFinal. Способ update употребляется, ежели вы шифруете либо расшифровываете фрагмент данных. Способ doFinal вызывается, когда вы шифруете крайний фрагмент данных либо ежели блок данных, который вы передаете в doFinal , является единичным набором данных для шифрования.

Чтоб расшифровать данные, необходимо передать зашифрованный текст данные в способ doFinal либо doUpdate. Для шифрования либо дешифрования данных для вас нужен ключ. Существует два типа ключей в зависимости от того, какой тип метода шифрования используется:.

Симметричные ключи употребляются для симметричных алгоритмов шифрования. Методы симметричного шифрования употребляют один и тот же ключ для шифрования и расшифровки. Асимметричные ключи употребляются для алгоритмов асимметричного шифрования. Методы асимметричного шифрования употребляют один ключ для шифрования, а иной для дешифрования. Методы шифрования с открытым и закрытым ключом — примеры асимметричных алгоритмов шифрования. Каким-то образом сторона, которая обязана расшифровать данные, обязана знать ключ, нужный для дешифрования данных.

Ежели дешифрующая сторона не является стороной шифрующей данные, эти две стороны должны договориться о ключе либо поменяться ключом. Это именуется обменом ключами. Ключи должны быть тяжело угадываемые, чтоб злодей не мог просто подобрать ключ шифрования. В примере из предшествующего раздела о классе Шифр Cipher употреблялся чрезвычайно обычной, агрессивно закодированный ключ. На практике так делать не стоит.

Ежели ключ сторон просто угадать, злодею будет просто расшифровать зашифрованные данные и, может быть, сделать поддельные сообщения без помощи других. Принципиально сделать ключ, который тяжело угадать. Таковым образом, ключ должен состоять из случайных байтов. Чем больше случайных байтов тем труднее угадать, поэтому что существует больше вероятных композиций. Чтоб сгенерировать случайные ключи шифрования вы сможете применять класс Java KeyGenerator. KeyGenerator будет наиболее тщательно описан в последующих главах, вот маленький пример его использования здесь:.

Методы асимметричного шифрования употребляют пару ключей, состоящую из открытого ключа и закрытого ключа, для шифрования и дешифрования данных. Для сотворения асимметричной пары ключей вы сможете применять KeyPairGenerator java. KeyPairGenerator будет наиболее тщательно описан в последующих главах, ниже обычной пример использования Java KeyPairGenerator:. Java KeyStore — это база данных, которая может содержать ключи. Java KeyStore представлен классом KeyStore java.

Хранилище ключей может содержать ключи последующих типов:. Закрытый и открытый ключи употребляются в асимметричном шифровании. Открытый ключ может иметь связанный сертификат. Сертификат — это документ, удостоверяющий личность человека, организации либо устройства, претендующего на владение открытым ключом. Сертификат традиционно имеет цифровую подпись проверяющей стороны в качестве подтверждения.

Скрытые ключи употребляются в симметричном шифровании. Класс KeyStore достаточно непростой, потому он описан наиболее тщательно дальше в отдельной главе по Java KeyStore. Java Keytool — это инструмент командной строчки, который может работать с файлами Java KeyStore.

Keytool может генерировать пары ключей в файл KeyStore, экспортировать сертификаты и импортировать сертификаты в KeyStore и некие остальные функции. Keytool поставляется с установкой Java. Keytool наиболее тщательно описан дальше в отдельной главе по Java Keytool. Когда вы получаете зашифрованные данные от иной стороны, сможете ли вы быть уверенными что никто не изменил зашифрованные данные по пути к вам?

Традиционно решение состоит в том, чтоб вычислить дайджест сообщения из данных до его шифрования, а потом зашифровать как данные, так и дайджест сообщения, и выслать его по сети. Дайджест сообщения — это хеш-значение, рассчитанное на базе данных сообщения. Ежели в зашифрованных данных меняется хоть один б поменяется и дайджест сообщения, рассчитанный по данным.

При получении зашифрованных данных вы расшифровываете их, вычисляете из их дайджест сообщения и сравниваете вычисленный дайджест сообщения с дайджестом сообщения, отправленного совместно с зашифрованными данными. Java MessageDigest java. MessageDigest можно применять для вычисления дайджестов сообщений. Для сотворения экземпляра MessageDigest вызывается способ MessageDigest. Существует несколько разных алгоритмов дайджеста сообщений.

Для вас необходимо указать, какой метод вы желаете употреблять при разработке экземпляра MessageDigest. В этом примере создается экземпляр MessageDigest, который употребляет внутренний метод криптографического хэширования SHA для вычисления дайджестов сообщений. Чтоб вычислить дайджест сообщения неких данных, вы вызываете способ update либо digest. Способ update может вызываться несколько раз, а дайджест сообщения обновляется снутри объекта.

Когда вы передали все данные, которые вы желаете включить в дайджест сообщения, вы вызываете digest и извлекаете итоговые данные дайджеста сообщения. Вы также сможете вызвать digest один раз, передав все данные, чтоб вычислить дайджест сообщения. MAC похож на дайджест сообщения, но употребляет доп ключ для шифрования дайджеста сообщения. Лишь имея как начальные данные, так и ключ, вы сможете проверить MAC. Вот пример шифрования пары блоков данных:.

Причина, по которой вызов doFinal нужен для крайнего блока данных, заключается в том, что некие методы шифрования должны дополнять данные, чтоб соответствовать определенному размеру блока шифра к примеру, 8-байтовой границе. Дополнять же промежные зашифрованные данные нет необходимости. Следовательно, вызывается способ update для промежных блоков данных и вызов doFinal для крайнего блока данных.

При расшифровке пары блоков данных вы также вызываете способ update для промежных блоков данных и способ doFinal для крайнего блока. Пример расшифровки пары блоков данных:. Снова же, экземпляр шифра должен быть инициализирован в режиме дешифровки, чтоб этот пример работал. Способы шифрования и расшифровки класса Cipher могут шифровать либо расшифровывать часть данных, хранящихся в байтовом массиве. В данном примере будут зашифрованы либо расшифрованы, в зависимости от инициализации шифра байты с 10 индекса и на 24 б вперед.

Все приведенные в данной для нас главе примеры шифрования и дешифрования возвращают зашифрованные либо дешифрованные данные в новеньком байтовом массиве. Но также может быть зашифровать либо расшифровать данные в имеющийся байтовый массив. Это может быть полезно для уменьшения количества сделанных байтовых массивов. В этом примере данные шифруются с 10 индекса на 24 б вперед в байтовый массив dest со смещением 0. Ежели вы желаете установить другое смещение для байтового массива dest, есть версии update и doFinal , которые принимают доп параметр смещения.

Пример вызова способа doFinal со смещением в массиве dest:. Инициализация экземпляра Cipher — дорогостоящая операция и неплохой идеей будет повторное внедрение экземпляров Cipher. К счастью, класс Cipher был разработан с учетом способности повторного использования.

Когда вы вызываете способ doFinal для экземпляра Cipher, он ворачивается в состояние, в котором находился сходу опосля инициализации. Экземпляр Cipher может потом употребляться для шифрования либо дешифрования большего количества данных. Поначалу создается и инициализируется экземпляр Cipher, а потом употребляется для шифрования 2-ух блоков согласованных данных.

Обратите внимание на вызов update , а потом doFinal для этих 2-ух блоков данных. Опосля этого экземпляр Cipher может быть опять применен для шифрования данных. Это делается с помощью вызова doFinal с третьим блоком данных. Опосля этого вызова doFinal вы сможете зашифровать еще один блок данных с тем же экземпляром Java Cipher. Поиск Профиль. Создание шифра До этого чем употреблять шифр, нужно сделать экземпляр класса Cipher , вызывая его способ getInstance с параметром, указывающим, какой тип метода шифрования вы желаете применять.

Режимы шифрования Некие методы шифрования могут работать в различных режимах. Инициализация шифра До этого чем употреблять экземпляр Cipher, его нужно инициализировать. Хабы: Криптография Программирование Java. Миша man41k. Комменты Комменты 3.

Java crypto обмен валюты на бирже сбербанка

СКРЫТЫЙ МАЙНЕР ПРОДАЖА

Many of the classes provided in this package are provider-based. The class itself defines a programming interface to which applications may write. The implementations themselves may then be written by independent third-party vendors and plugged in seamlessly as needed. Therefore application developers may take advantage of any number of provider-based implementations without having to add or rewrite code. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

All rights reserved. Use is subject to license terms. Also see the documentation redistribution policy. Skip navigation links. Package javax. This class provides the functionality of a cryptographic cipher for encryption and decryption. A CipherInputStream is composed of an InputStream and a Cipher so that read methods return data that are read in from the underlying InputStream but have been additionally processed by the Cipher.

A CipherOutputStream is composed of an OutputStream and a Cipher so that write methods first process the data before writing them out to the underlying OutputStream. The verify method returns a boolean indicating whether or not the encoded signature is the authentic signature of the data supplied to the update method s. A call to the verify method resets the signature object to its state when it was initialized for verification via a call to initVerify.

That is, the object is reset and available to verify another signature from the identity whose public key was specified in the call to initVerify. Alternatively, a new call can be made to initVerify specifying a different public key to initialize the Signature object for verifying a signature from a different entity , or to initSign to initialize the Signature object for generating a signature.

The Cipher class provides the functionality of a cryptographic cipher used for encryption and decryption. Encryption is the process of taking data called cleartext and a key , and producing data ciphertext meaningless to a third-party who does not know the key.

Decryption is the inverse process: that of taking ciphertext and a key and producing cleartext. Asymmetric Cryptography There are two major types of encryption: symmetric also known as secret key , and asymmetric or public key cryptography.

In symmetric cryptography, the same secret key to both encrypt and decrypt the data. Keeping the key private is critical to keeping the data confidential. Data encrypted with one key is decrypted with the other. A user who wishes to communicate securely with that user encrypts the data using the retrieved public key.

Only the holder of the private key will be able to decrypt. Keeping the private key confidential is critical to this scheme. Asymmetric algorithms such as RSA are generally much slower than symmetric ones. These algorithms are not designed for efficiently protecting large amounts of data. In practice, asymmetric algorithms are used to exchange smaller secret keys which are used to initialize symmetric algorithms.

When encrypting using a simple block cipher, two identical blocks of plaintext will always produce an identical block of cipher text. Cryptanalysts trying to break the ciphertext will have an easier job if they note blocks of repeating text. In order to add more complexity to the text, feedback modes use the previous block of output to alter the input blocks before applying the encryption algorithm.

The first block will need an initial value, and this value is called the initialization vector IV. Since the IV simply alters the data before any encryption, the IV should be random but does not necessarily need to be kept secret. ECB Electronic Codebook Mode is a mode in which there is no influence from block position or other ciphertext blocks. Encryption using a longer key generally implies a stronger resistance to message recovery. As usual, there is a trade off between security and time, so choose the key length appropriately.

Most algorithms use binary keys. Most humans do not have the ability to remember long sequences of binary numbers, even when represented in hexadecimal. Character passwords are much easier to recall. Because character passwords are generally chosen from a small number of characters for example, [a-zA-Z] , protocols such as "Password-Based Encryption" PBE have been defined which take character passwords and generate strong binary keys.

For example, some data might not need to be kept confidential, but should figure into the tag calculation to detect modifications. The Cipher. If just a transformation name is specified, the system will determine if there is an implementation of the requested transformation available in the environment, and if there is more than one, returns there is a preferred one.

If both a transformation name and a package provider are specified, the system will determine if there is an implementation of the requested transformation in the package requested, and throw an exception if there is not. It is recommended to use a transformation that fully specifies the algorithm, mode, and padding. By not doing so, the provider will use a default.

ECB works well for single blocks of data, but absolutely should not be used for multiple data blocks. If no such number is specified, a provider-specific default is used. Appendix A of this document contains a list of standard names that can be used to specify the algorithm name, mode, and padding scheme components of a transformation. The objects returned by factory methods are uninitialized, and must be initialized before they become usable. A Cipher object obtained via getInstance must be initialized for one of four modes, which are defined as final integer constants in the Cipher class.

The modes can be referenced by their symbolic names, which are shown below along with a description of the purpose of each mode:. Each of the Cipher initialization methods takes an operational mode parameter opmode , and initializes the Cipher object for that mode. Other parameters include the key key or certificate containing the key certificate , algorithm parameters params , and a source of randomness random.

If a Cipher object that requires parameters e. However, if a Cipher object that requires parameters is initialized for decryption, and no parameters are supplied to the init method, an InvalidKeyException or InvalidAlgorithmParameterException exception will be raised, depending on the init method that has been used. See the section about Managing Algorithm Parameters for more details.

Note that when a Cipher object is initialized, it loses all previously-acquired state. In other words, initializing a Cipher is equivalent to creating a new instance of that Cipher, and initializing it. For example, if a Cipher is first initialized for decryption with a given key, and then initialized for encryption, it will lose any state acquired while in decryption mode. Data can be encrypted or decrypted in one step single-part operation or in multiple steps multiple-part operation.

A multiple-part operation is useful if you do not know in advance how long the data is going to be, or if the data is too long to be stored in memory all at once. A multiple-part operation must be terminated by one of the above doFinal methods if there is still some input data left for the last step , or by one of the following doFinal methods if there is no input data left for the last step :. All the doFinal methods take care of any necessary padding or unpadding , if padding or unpadding has been requested as part of the specified transformation.

A call to doFinal resets the Cipher object to the state it was in when initialized via a call to init. That is, the Cipher object is reset and available to encrypt or decrypt depending on the operation mode that was specified in the call to init more data. These methods also enable the possibility of secure transfer of hardware-based keys. If you are supplying the wrapped key bytes the result of calling wrap to someone else who will unwrap them, be sure to also send additional information the recipient will need in order to do the unwrap :.

The key algorithm name can be determined by calling the getAlgorithm method from the Key interface:. Here, wrappedKey is the bytes returned from the previous call to wrap, wrappedKeyAlgorithm is the algorithm associated with the wrapped key, and wrappedKeyType is the type of the wrapped key.

This must be one of Cipher. The parameters being used by the underlying Cipher implementation, which were either explicitly passed to the init method by the application or generated by the underlying implementation itself, can be retrieved from the Cipher object by calling its getParameters method, which returns the parameters as a java. AlgorithmParameters object or null if no parameters are being used. If the parameter is an initialization vector IV , it can also be retrieved by calling the getIV method.

In the following example, a Cipher object implementing password-based encryption PBE is initialized with just a key and no parameters. However, the selected algorithm for password-based encryption requires two parameters - a salt and an iteration count. Those will be generated by the underlying algorithm implementation itself. The application can retrieve the generated parameters from the Cipher object as follows:.

The same parameters that were used for encryption must be used for decryption. They can be instantiated from their encoding and used to initialize the corresponding Cipher object for decryption, as follows:. If you did not specify any parameters when you initialized a Cipher object, and you are not sure whether or not the underlying implementation uses any parameters, you can find out by simply calling the getParameters method of your Cipher object and checking the value returned. A return value of null indicates that no parameters were used.

Note that you do not have to worry about storing or transferring any algorithm parameters for use by the decryption operation if you use the SealedObject class. This class attaches the parameters used for sealing encryption to the encrypted object contents, and uses the same parameters for unsealing decryption. Some of the update and doFinal methods of Cipher allow the caller to specify the output buffer into which to encrypt or decrypt the data.

In these cases, it is important to pass a buffer that is large enough to hold the result of the encryption or decryption operation. This class is a FilterInputStream that encrypts or decrypts the data passing through it. It is composed of an InputStream , or one of its subclasses, and a Cipher. CipherInputStream represents a secure input stream into which a Cipher object has been interposed.

The read methods of CipherInputStream return data that are read from the underlying InputStream but have additionally been processed by the embedded Cipher object. The Cipher object must be fully initialized before being used by a CipherInputStream. For example, if the embedded Cipher has been initialized for decryption, the CipherInputStream will attempt to decrypt the data it reads from the underlying InputStream before returning them to the application. This class adheres strictly to the semantics, especially the failure semantics, of its ancestor classes java.

FilterInputStream and java. This class has exactly those methods specified in its ancestor classes, and overrides them all, so that the data are additionally processed by the embedded cipher. Moreover, this class catches all exceptions that are not thrown by its ancestor classes. In particular, the skip long method skips only data that has been processed by the Cipher.

It is crucial for a programmer using this class not to use methods that are not defined or overridden in this class such as a new method or constructor that is later added to one of the super classes , because the design and implementation of those methods are unlikely to have considered security impact with regard to CipherInputStream. As an example of its usage, suppose cipher1 has been initialized for encryption.

The code below demonstrates how to use a CipherInputStream containing that cipher and a FileInputStream in order to encrypt input stream data:. In this example, assume that cipher1 and cipher2 have been initialized for encryption and decryption with corresponding keys , respectively.

Note that the read methods of the CipherInputStream will block until data is returned from the underlying cipher. If a block cipher is used, a full block of cipher text will have to be obtained from the underlying InputStream. This class is a FilterOutputStream that encrypts or decrypts the data passing through it. It is composed of an OutputStream , or one of its subclasses, and a Cipher. CipherOutputStream represents a secure output stream into which a Cipher object has been interposed.

The write methods of CipherOutputStream first process the data with the embedded Cipher object before writing them out to the underlying OutputStream. The Cipher object must be fully initialized before being used by a CipherOutputStream. For example, if the embedded Cipher has been initialized for encryption, the CipherOutputStream will encrypt its data, before writing them out to the underlying output stream. OutputStream and java.

This class has exactly those methods specified in its ancestor classes, and overrides them all, so that all data are additionally processed by the embedded cipher. It is crucial for a programmer using this class not to use methods that are not defined or overridden in this class such as a new method or constructor that is later added to one of the super classes , because the design and implementation of those methods are unlikely to have considered security impact with regard to CipherOutputStream.

The code below demonstrates how to use a CipherOutputStream containing that cipher and a FileOutputStream in order to encrypt data to be written to an output stream:. The following example demonstrates how to easily connect several instances of CipherOutputStream and FileOutputStream. In this example, assume that cipher1 and cipher2 have been initialized for decryption and encryption with corresponding keys , respectively:. One thing to keep in mind when using block cipher algorithms is that a full block of plaintext data must be given to the CipherOutputStream before the data will be encrypted and sent to the underlying output stream.

There is one other important difference between the flush and close methods of this class, which becomes even more relevant if the encapsulated Cipher object implements a block cipher algorithm with padding turned on:. This class enables a programmer to create an object and protect its confidentiality with a cryptographic algorithm. Given any object that implements the java. Serializable interface, one can create a SealedObject that encapsulates the original object, in serialized format i.

The encrypted content can later be decrypted with the corresponding algorithm using the correct decryption key and deserialized, yielding the original object. A typical usage is illustrated in the following code segment: In order to seal an object, you create a SealedObject from the object to be sealed and a fully initialized Cipher object that will encrypt the serialized object contents.

Note that any algorithm parameters that may be used in the sealing operation are stored inside of SealedObject :. This approach has the advantage that the party who unseals the sealed object does not require knowledge of the decryption key.

For example, after one party has initialized the cipher object with the required decryption key, it could hand over the cipher object to another party who then unseals the sealed object. In this approach, the getObject method creates a cipher object for the appropriate decryption algorithm and initializes it with the given decryption key and the algorithm parameters if any that were stored in the sealed object.

This approach has the advantage that the party who unseals the object does not need to keep track of the parameters e. Similar to a MessageDigest , a Message Authentication Code MAC provides a way to check the integrity of information transmitted over or stored in an unreliable medium, but includes a secret key in the calculation. Only someone with the proper key will be able to verify the received message.

Typically, message authentication codes are used between two parties that share a secret key in order to validate information transmitted between these parties. HMAC can be used with any cryptographic hash function, e. Please refer to the code example. A Mac object is always initialized with a secret key and may optionally be initialized with a set of parameters, depending on the underlying MAC algorithm.

You can initialize your Mac object with any secret- key object that implements the javax. SecretKey interface. This could be an object returned by javax. With others, however, the secret- key algorithm does matter, and an InvalidKeyException is thrown if a secret- key object with an inappropriate secret- key algorithm is used. A MAC can be computed in one step single-part operation or in multiple steps multiple-part operation. To compute the MAC of some data in a single step, call the following doFinal method:.

A multiple-part operation must be terminated by the above doFinal method if there is still some input data left for the last step , or by one of the following doFinal methods if there is no input data left for the last step :. It is now time to turn our attention to keys. The java. Key interface is the top-level interface for all opaque keys. It defines the functionality shared by all opaque key objects. An opaque key representation is one in which you have no direct access to the key material that constitutes a key.

In other words: "opaque" gives you limited access to the key--just the three methods defined by the Key interface see below : getAlgorithm , getFormat , and getEncoded. This is in contrast to a transparent representation, in which you can access each key material value individually, through one of the get methods defined in the corresponding specification class.

It is also possible to parse certificates, using a CertificateFactory. Here is a list of interfaces which extend the Key interface in the java. The PublicKey and PrivateKey interfaces which both extend the Key interface are methodless interfaces, used for type-safety and type-identification. The KeyPair class is a simple holder for a key pair a public key and a private key. It has two public methods, one for returning the private key, and the other for returning the public key:.

Key objects and key specifications KeySpec s are two different representations of key data. Cipher s use Key objects to initialize their encryption algorithms, but keys may need to be converted into a more portable format for transmission or storage. A transparent representation of keys means that you can access each key material value individually, through one of the get methods defined in the corresponding specification class.

If the key is stored on a hardware device, its specification may contain information that helps identify the key on the device. This representation is contrasted with an opaque representation, as defined by the Key interface, in which you have no direct access to the key material fields. In other words, an "opaque" representation gives you limited access to the key--just the three methods defined by the Key interface: getAlgorithm , getFormat , and getEncoded.

A key may be specified in an algorithm-specific way, or in an algorithm-independent encoding format such as ASN. The KeyFactory and SecretKeyFactory classes can be used to convert between opaque and transparent key representations that is, between Key s and KeySpec s, assuming that the operation is possible.

For example, private keys on smart cards might not be able leave the card. Such Key s are not convertible. In the following sections, we discuss the key specification interfaces and classes in the java. This interface contains no methods or constants. Its only purpose is to group and provide type safety for all key specifications.

All key specifications must implement this interface. Generators are used to generate brand new objects. Generators can be initialized in either an algorithm-dependent or algorithm-independent way. For example, to create a Diffie-Hellman DH keypair, an application could specify the necessary P and G values, or the generator could simply be initialized with the appropriate key length, and the generator will select appropriate P and G values. In both cases, the generator will produce brand new keys based on the parameters.

On the other hand, factories are used to convert data from one existing object type to another. For example, an application might have available the components of a DH private key and can package them as a KeySpec , but needs to convert them into a PrivateKey object that can be used by a KeyAgreement object, or vice-versa. Or they might have the byte array of a certificate, but need to use a CertificateFactory to convert it into a XCertificate object. Applications use factory objects to do the conversion.

The KeyFactory class is an engine class designed to perform conversions between opaque cryptographic Key s and key specifications transparent representations of the underlying key material. Key factories are bidirectional. They allow you to build an opaque key object from a given key specification key material , or to retrieve the underlying key material of a key object in a suitable format.

Multiple compatible key specifications can exist for the same key. For example, a DSA public key may be specified by its components y , p , q , and g see java. A key factory can be used to translate between compatible key specifications.

Key parsing can be achieved through translation between compatible key specifications, e. KeyFactory objects are obtained by using one of the KeyFactory getInstance static factory methods. If you have a key specification for a public key, you can obtain an opaque PublicKey object from the specification by using the generatePublic method:.

Similarly, if you have a key specification for a private key, you can obtain an opaque PrivateKey object from the specification by using the generatePrivate method:. If you have a Key object, you can get a corresponding key specification object by calling the getKeySpec method:. This class represents a factory for secret keys. Unlike KeyFactory , a javax.

SecretKeyFactory object operates only on secret symmetric keys, whereas a java. KeyFactory object processes the public and private key components of a key pair. Key factories are used to convert Key s opaque cryptographic keys of type java. Key into key specifications transparent representations of the underlying key material in a suitable format , and vice versa. Objects of type java. Key , of which java. PublicKey , java. PrivateKey , and javax.

SecretKey are subclasses, are opaque key objects, because you cannot tell how they are implemented. The underlying implementation is provider-dependent, and may be software or hardware based. Key factories allow providers to supply their own implementations of cryptographic keys.

For example, if you have a key specification for a Diffie Hellman public key, consisting of the public value y , the prime modulus p , and the base g , and you feed the same specification to Diffie-Hellman key factories from different providers, the resulting PublicKey objects will most likely have different underlying implementations.

A provider should document the key specifications supported by its secret key factory. The following is an example of how to use a SecretKeyFactory to convert secret key data into a SecretKey object, which can be used for a subsequent Cipher operation:. In this case, the underlying implementation of SecretKey is based on the provider of KeyFactory. An alternative, provider-independent way of creating a functionally equivalent SecretKey object from the same key material is to use the javax.

SecretKeySpec class, which implements the javax. SecretKey interface:. If you have a key specification for a secret key, you can obtain an opaque SecretKey object from the specification by using the generateSecret method:. If you have a Secret Key object, you can get a corresponding key specification object by calling the getKeySpec method:. The KeyPairGenerator class is an engine class used to generate pairs of public and private keys.

There are two ways to generate a key pair: in an algorithm-independent manner, and in an algorithm-specific manner. The only difference between the two is the initialization of the object. Please see the Examples section for examples of calls to the methods documented below. All key pair generation starts with a KeyPairGenerator. A key pair generator needs to be initialized before it can generate keys.

In most cases, algorithm-independent initialization is sufficient. But in other cases, algorithm-specific initialization can be used. All key pair generators share the concepts of a keysize and a source of randomness. The keysize is interpreted differently for different algorithms.

For example, in the case of the DSA algorithm, the keysize corresponds to the length of the modulus. See the Standard Names document for information about the keysizes for specific algorithms. Since no other parameters are specified when you call the above algorithm-independent initialize methods, it is up to the provider what to do about the algorithm-specific parameters if any to be associated with each of the keys.

If the algorithm is a "DSA" algorithm, and the modulus size keysize is , , or , then the SUN provider uses a set of precomputed values for the p , q , and g parameters. If the modulus size is not one of the above values, the SUN provider creates a new set of parameters. Other providers might have precomputed parameter sets for more than just the three modulus sizes mentioned above.

Still others might not have a list of precomputed parameters at all and instead always create new parameter sets. For situations where a set of algorithm-specific parameters already exists such as "community parameters" in DSA , there are two initialize methods that have an AlgorithmParameterSpec argument. One also has a SecureRandom argument, while the source of randomness is system-provided for the other:.

The procedure for generating a key pair is always the same, regardless of initialization and of the algorithm. You always call the following method from KeyPairGenerator :. A key generator for a particular symmetric-key algorithm creates a symmetric key that can be used with that algorithm. It also associates algorithm-specific parameters if any with the generated key.

There are two ways to generate a key: in an algorithm-independent manner, and in an algorithm-specific manner. The only difference between the two is the initialization of the object:. All key generators share the concepts of a keysize and a source of randomness.

There is an init method that takes these two universally shared types of arguments. There is also one that takes just a keysize argument, and uses a system-provided source of randomness, and one that takes just a source of randomness:. Since no other parameters are specified when you call the above algorithm-independent init methods, it is up to the provider what to do about the algorithm-specific parameters if any to be associated with the generated key.

For situations where a set of algorithm-specific parameters already exists, there are two init methods that have an AlgorithmParameterSpec argument. In case the client does not explicitly initialize the KeyGenerator via a call to an init method , each provider must supply and document a default initialization. Key agreement is a protocol by which 2 or more parties can establish the same cryptographic keys, without having to exchange any secret information.

Each party initializes their key agreement object with their private key, and then enters the public keys for each party that will participate in the communication. In most cases, there are just two parties, but algorithms such as Diffie-Hellman allow for multiple parties 3 or more to participate. When all the public keys have been entered, each KeyAgreement object will generate agree upon the same key. The KeyAgreement class provides the functionality of a key agreement protocol.

The keys involved in establishing a shared secret are created by one of the key generators KeyPairGenerator or KeyGenerator , a KeyFactory , or as a result from an intermediate phase of the key agreement protocol. Each party involved in the key agreement has to create a KeyAgreement object. KeyAgreement objects are obtained by using one of the KeyAgreement getInstance static factory methods. You initialize a KeyAgreement object with your private information. In the case of Diffie-Hellman, you initialize it with your Diffie-Hellman private key.

Note that if the requested key agreement algorithm requires the specification of algorithm parameters, and only a key, but no parameters are provided to initialize the KeyAgreement object, the key must contain the required algorithm parameters. For example, the Diffie-Hellman algorithm uses a prime modulus p and a base generator g as its parameters. Every key agreement protocol consists of a number of phases that need to be executed by each party involved in the key agreement.

The key parameter contains the key to be processed by that phase. In most cases, this is the public key of one of the other parties involved in the key agreement, or an intermediate key that was generated by a previous phase. The lastPhase parameter specifies whether or not the phase to be executed is the last one in the key agreement: A value of FALSE indicates that this is not the last phase of the key agreement there are more phases to follow , and a value of TRUE indicates that this is the last phase of the key agreement and the key agreement is completed, i.

After each party has executed all the required key agreement phases, it can compute the shared secret by calling one of the generateSecret methods:. The user keystore is by default stored in a file named. On Solaris systems "user.

On Win32 systems, given user name uName , "user. These CA certificates can be used to help make trust decisions. Instead of using the system-wide cacerts keystore, applications can set up and use their own keystores, or even use the user keystore described above. Currently, there are two command-line tools that make use of KeyStore : keytool and jarsigner , and also a GUI-based tool named policytool.

It is also used by the Policy reference implementation when it processes policy files specifying the permissions allowed accesses to system resources to be granted to code from various sources. Since KeyStore is publicly available, JDK users can write additional security applications that use it.

Applications can choose different types of keystore implementations from different providers, using the getInstance factory method in the KeyStore class. A keystore type defines the storage and data format of the keystore information, and the algorithms used to protect private keys in the keystore and the integrity of the keystore itself.

Keystore implementations of different types are not compatible. The recommended keystore implementation is "pkcs12". Arbitrary attributes can be associated with individual entries in a PKCS12 keystore. The default keystore implementation type is "jks", which is specified in the following line in the java. To have tools and other applications use a different default keystore implementation, you can change that line to specify another default type.

For example, to use "pkcs12" as the default keystore implementation, change the line to:. Some applications, such as keytool , also let you override the default keystore type via the -storetype command-line parameter.

The "jceks" implementation can parse and convert a "jks" keystore file to the "jceks" format. You may upgrade your keystore of type "jks" to a keystore of type "jceks" by changing the password of a private-key entry in your keystore and specifying -storetype jceks as the keystore type. To apply the cryptographically strong er key protection supplied to a private key named "signkey" in your default keystore, use the following command, which will prompt you for the old and new key passwords:.

See Security Tools for more information about keytool and about keystores and how they are managed. Keystore implementations are provider-based. Developers interested in writing their own KeyStore implementations should consult How to Implement a Provider for the Java Cryptography Architecture for more information on this topic.

The KeyStore class is an engine class that supplies well-defined interfaces to access and modify the information in a keystore. This class represents an in-memory collection of keys and certificates. KeyStore manages two types of entries:. This type of keystore entry holds very sensitive cryptographic key information, which is stored in a protected format to prevent unauthorized access.

Typically, a key stored in this type of entry is a secret key, or a private key accompanied by the certificate chain authenticating the corresponding public key. Private keys and certificate chains are used by a given entity for self-authentication using digital signatures. This type of entry contains a single public key certificate belonging to another party. It is called a trusted certificate because the keystore owner trusts that the public key in the certificate indeed belongs to the identity identified by the subject owner of the certificate.

Whether keystores are persistent, and the mechanisms used by the keystore if it is persistent, are not specified here. This convention allows use of a variety of techniques for protecting sensitive e. Smart cards or other integrated cryptographic engines SafeKeyper are one option, and simpler mechanisms such as files may also be used in a variety of formats.

KeyStore objects are obtained by using one of the KeyStore getInstance static factory methods. To create an empty keystore, you pass null as the InputStream argument to the load method. All keystore entries are accessed via unique aliases. The aliases method returns an enumeration of the alias names in the keystore:. A transparent representation of a set of parameters via AlgorithmParameterSpec means that you can access each parameter value in the set individually.

You can access these values through one of the get methods defined in the corresponding specification class e. In contrast, the AlgorithmParameters class supplies an opaque representation, in which you have no direct access to the parameter fields. You can only get the name of the algorithm associated with the parameter set via getAlgorithm and some kind of encoding for the parameter set via getEncoded. The algorithm parameter specification interfaces and classes in the java.

The following algorithm parameter specs are used specifically for digital signatures, as part of JSR AlgorithmParameters objects are obtained by using one of the AlgorithmParameters getInstance static factory methods. Once an AlgorithmParameters object is instantiated, it must be initialized via a call to init , using an appropriate parameter specification or parameter encoding:. A byte encoding of the parameters represented in an AlgorithmParameters object may be obtained via a call to getEncoded :.

A transparent parameter specification for the algorithm parameters may be obtained from an AlgorithmParameters object via a call to getParameterSpec :. AlgorithmParameterGenerator objects are obtained by using one of the AlgorithmParameterGenerator getInstance static factory methods. The AlgorithmParameterGenerator object can be initialized in two different ways: an algorithm-independent manner or an algorithm-specific manner.

The algorithm-independent approach uses the fact that all parameter generators share the concept of a "size" and a source of randomness. The measure of size is universally shared by all algorithm parameters, though it is interpreted differently for different algorithms. For example, in the case of parameters for the DSA algorithm, "size" corresponds to the size of the prime modulus, in bits.

See the Standard Names document for information about the sizes for specific algorithms. When using this approach, algorithm-specific parameter generation values--if any--default to some standard values. One init method that takes these two universally shared types of arguments:. A third approach initializes a parameter generator object using algorithm-specific semantics, which are represented by a set of algorithm-specific parameter generation values supplied in an AlgorithmParameterSpec object:.

A certificate factory for X. XCertificate , and CRLs that are an instance of java. CertificateFactory objects are obtained by using one of the getInstance static factory methods. To generate a CertPath object and initialize it with data read from an input stream, use one of the following generateCertPath methods with or without specifying the encoding to be used for the data :.

This provider mainly provides a mapping from algorithm names to actual implementation classes. SSLContext s are initialized with two callback classes, KeyManager and TrustManager , which allow applications to first select authentication material to send and second to verify credentials sent by a peer. When a credential is needed, the KeyManager simply consults this KeyStore object and determines which credentials to present. This generator is then used to create a KeyPair which keytool would store along with the newly-created certificate in the KeyStore , which is eventually written to disk.

Internally, the CertPath implementation might create a Signature object, and use that to verify that the each of the signatures in the certificate chain. The client begins by sending a ClientHello message to the server. The server selects a ciphersuite to use, and sends that back in a ServerHello message, and begins creating JCA objects based on the suite selection.

This encrypted data is sent in a Client Key Exchange message. The server would use its corresponding PrivateKey to recover the bytes using a similar Cipher in decrypt mode. These bytes are then used to establish the actual encryption keys. The server sends its public key pieces in a ServerKeyExchange message protected by the DSA signature algorithm, and the client sends its public key in a ClientKeyExchange message. When the public keys are reassembled using another KeyFactory , they are fed into the agreement objects.

The KeyAgreement objects then generate agreed-upon bytes that are then used to establish the actual encryption keys. Once the actual encryption keys have been established, the secret key is used to initialize a symmetric Cipher object, and this cipher is used to protect all data in transit.

To help determine if the data has been modified, a MessageDigest is created and receives a copy of the data destined for the network. When the packet is complete, the digest hash is appended to data, and the entire packet is encrypted by the Cipher. If a block cipher such as AES is used, the data must be padded to make a complete block.

On the remote side, the steps are simply reversed. Again, this is vastly simplified, but gives one an idea of how these classes might be combined to create a higher level protocol. Note : This section should be ignored by most application developers. It is only for people whose applications may be exported to those few countries whose governments mandate cryptographic restrictions, if it is desired that such applications have fewer cryptographic restrictions than those mandated.

By default, an application can use cryptographic algorithms of any strength. The JCA framework includes an ability to enforce restrictions regarding the maximum strengths of cryptographic algorithms available to applications in different jurisdiction contexts locations. You specify these restrictions in jurisdiction policy files.

It is possible that the governments of some or all such countries may allow certain applications to become exempt from some or all cryptographic restrictions.

Java crypto не могу запустить майнер

Java Encryption and Decryption Tutorial (Basic)

Вам miami dash моему мнению

java crypto

MAINNET TRON

This class provides the functionality of a cryptographic cipher for encryption and decryption. A CipherInputStream is composed of an InputStream and a Cipher so that read methods return data that are read in from the underlying InputStream but have been additionally processed by the Cipher.

A CipherOutputStream is composed of an OutputStream and a Cipher so that write methods first process the data before writing them out to the underlying OutputStream. This class provides the functionality of an exemption mechanism, examples of which are key recovery , key weakening , and key escrow.

This class provides the functionality of a key agreement or key exchange protocol. The NullCipher class is a class that provides an "identity cipher" -- one that does not tranform the plaintext. This class enables a programmer to create an object and protect its confidentiality with a cryptographic algorithm.

This exception is thrown when a particular padding mechanism is expected for the input data but the data is not padded properly. This exception is thrown when the length of data provided to a block cipher is incorrect, i. This exception is thrown when a particular padding mechanism is requested but is not available in the environment. This exception is thrown when an output buffer provided by the user is too short to hold the operation result. Provides the classes and interfaces for cryptographic operations.

For example, if the embedded Cipher has been initialized for decryption, the CipherInputStream will attempt to decrypt the data it reads from the underlying InputStream before returning them to the application. This class adheres strictly to the semantics, especially the failure semantics, of its ancestor classes java.

FilterInputStream and java. This class has exactly those methods specified in its ancestor classes, and overrides them all, so that the data are additionally processed by the embedded cipher. Moreover, this class catches all exceptions that are not thrown by its ancestor classes. In particular, the skip long method skips only data that has been processed by the Cipher. It is crucial for a programmer using this class not to use methods that are not defined or overridden in this class such as a new method or constructor that is later added to one of the super classes , because the design and implementation of those methods are unlikely to have considered security impact with regard to CipherInputStream.

As an example of its usage, suppose cipher1 has been initialized for encryption. The code below demonstrates how to use a CipherInputStream containing that cipher and a FileInputStream in order to encrypt input stream data:. In this example, assume that cipher1 and cipher2 have been initialized for encryption and decryption with corresponding keys , respectively.

Note that the read methods of the CipherInputStream will block until data is returned from the underlying cipher. If a block cipher is used, a full block of cipher text will have to be obtained from the underlying InputStream.

This class is a FilterOutputStream that encrypts or decrypts the data passing through it. It is composed of an OutputStream , or one of its subclasses, and a Cipher. CipherOutputStream represents a secure output stream into which a Cipher object has been interposed. The write methods of CipherOutputStream first process the data with the embedded Cipher object before writing them out to the underlying OutputStream. The Cipher object must be fully initialized before being used by a CipherOutputStream.

For example, if the embedded Cipher has been initialized for encryption, the CipherOutputStream will encrypt its data, before writing them out to the underlying output stream. OutputStream and java. This class has exactly those methods specified in its ancestor classes, and overrides them all, so that all data are additionally processed by the embedded cipher.

It is crucial for a programmer using this class not to use methods that are not defined or overridden in this class such as a new method or constructor that is later added to one of the super classes , because the design and implementation of those methods are unlikely to have considered security impact with regard to CipherOutputStream.

The code below demonstrates how to use a CipherOutputStream containing that cipher and a FileOutputStream in order to encrypt data to be written to an output stream:. The following example demonstrates how to easily connect several instances of CipherOutputStream and FileOutputStream. In this example, assume that cipher1 and cipher2 have been initialized for decryption and encryption with corresponding keys , respectively:.

One thing to keep in mind when using block cipher algorithms is that a full block of plaintext data must be given to the CipherOutputStream before the data will be encrypted and sent to the underlying output stream. There is one other important difference between the flush and close methods of this class, which becomes even more relevant if the encapsulated Cipher object implements a block cipher algorithm with padding turned on:.

This class enables a programmer to create an object and protect its confidentiality with a cryptographic algorithm. Given any object that implements the java. Serializable interface, one can create a SealedObject that encapsulates the original object, in serialized format i.

The encrypted content can later be decrypted with the corresponding algorithm using the correct decryption key and deserialized, yielding the original object. A typical usage is illustrated in the following code segment: In order to seal an object, you create a SealedObject from the object to be sealed and a fully initialized Cipher object that will encrypt the serialized object contents.

Note that any algorithm parameters that may be used in the sealing operation are stored inside of SealedObject :. This approach has the advantage that the party who unseals the sealed object does not require knowledge of the decryption key. For example, after one party has initialized the cipher object with the required decryption key, it could hand over the cipher object to another party who then unseals the sealed object.

In this approach, the getObject method creates a cipher object for the appropriate decryption algorithm and initializes it with the given decryption key and the algorithm parameters if any that were stored in the sealed object. This approach has the advantage that the party who unseals the object does not need to keep track of the parameters e.

Similar to a MessageDigest , a Message Authentication Code MAC provides a way to check the integrity of information transmitted over or stored in an unreliable medium, but includes a secret key in the calculation. Only someone with the proper key will be able to verify the received message. Typically, message authentication codes are used between two parties that share a secret key in order to validate information transmitted between these parties.

HMAC can be used with any cryptographic hash function, e. Please refer to the code example. A Mac object is always initialized with a secret key and may optionally be initialized with a set of parameters, depending on the underlying MAC algorithm. You can initialize your Mac object with any secret- key object that implements the javax.

SecretKey interface. This could be an object returned by javax. With others, however, the secret- key algorithm does matter, and an InvalidKeyException is thrown if a secret- key object with an inappropriate secret- key algorithm is used. A MAC can be computed in one step single-part operation or in multiple steps multiple-part operation. To compute the MAC of some data in a single step, call the following doFinal method:.

A multiple-part operation must be terminated by the above doFinal method if there is still some input data left for the last step , or by one of the following doFinal methods if there is no input data left for the last step :. It is now time to turn our attention to keys. The java. Key interface is the top-level interface for all opaque keys.

It defines the functionality shared by all opaque key objects. An opaque key representation is one in which you have no direct access to the key material that constitutes a key. In other words: "opaque" gives you limited access to the key--just the three methods defined by the Key interface see below : getAlgorithm , getFormat , and getEncoded. This is in contrast to a transparent representation, in which you can access each key material value individually, through one of the get methods defined in the corresponding specification class.

It is also possible to parse certificates, using a CertificateFactory. Here is a list of interfaces which extend the Key interface in the java. The PublicKey and PrivateKey interfaces which both extend the Key interface are methodless interfaces, used for type-safety and type-identification. The KeyPair class is a simple holder for a key pair a public key and a private key. It has two public methods, one for returning the private key, and the other for returning the public key:.

Key objects and key specifications KeySpec s are two different representations of key data. Cipher s use Key objects to initialize their encryption algorithms, but keys may need to be converted into a more portable format for transmission or storage. A transparent representation of keys means that you can access each key material value individually, through one of the get methods defined in the corresponding specification class. If the key is stored on a hardware device, its specification may contain information that helps identify the key on the device.

This representation is contrasted with an opaque representation, as defined by the Key interface, in which you have no direct access to the key material fields. In other words, an "opaque" representation gives you limited access to the key--just the three methods defined by the Key interface: getAlgorithm , getFormat , and getEncoded. A key may be specified in an algorithm-specific way, or in an algorithm-independent encoding format such as ASN.

The KeyFactory and SecretKeyFactory classes can be used to convert between opaque and transparent key representations that is, between Key s and KeySpec s, assuming that the operation is possible. For example, private keys on smart cards might not be able leave the card. Such Key s are not convertible.

In the following sections, we discuss the key specification interfaces and classes in the java. This interface contains no methods or constants. Its only purpose is to group and provide type safety for all key specifications. All key specifications must implement this interface. Generators are used to generate brand new objects. Generators can be initialized in either an algorithm-dependent or algorithm-independent way. For example, to create a Diffie-Hellman DH keypair, an application could specify the necessary P and G values, or the generator could simply be initialized with the appropriate key length, and the generator will select appropriate P and G values.

In both cases, the generator will produce brand new keys based on the parameters. On the other hand, factories are used to convert data from one existing object type to another. For example, an application might have available the components of a DH private key and can package them as a KeySpec , but needs to convert them into a PrivateKey object that can be used by a KeyAgreement object, or vice-versa.

Or they might have the byte array of a certificate, but need to use a CertificateFactory to convert it into a XCertificate object. Applications use factory objects to do the conversion. The KeyFactory class is an engine class designed to perform conversions between opaque cryptographic Key s and key specifications transparent representations of the underlying key material.

Key factories are bidirectional. They allow you to build an opaque key object from a given key specification key material , or to retrieve the underlying key material of a key object in a suitable format. Multiple compatible key specifications can exist for the same key.

For example, a DSA public key may be specified by its components y , p , q , and g see java. A key factory can be used to translate between compatible key specifications. Key parsing can be achieved through translation between compatible key specifications, e. KeyFactory objects are obtained by using one of the KeyFactory getInstance static factory methods. If you have a key specification for a public key, you can obtain an opaque PublicKey object from the specification by using the generatePublic method:.

Similarly, if you have a key specification for a private key, you can obtain an opaque PrivateKey object from the specification by using the generatePrivate method:. If you have a Key object, you can get a corresponding key specification object by calling the getKeySpec method:. This class represents a factory for secret keys. Unlike KeyFactory , a javax. SecretKeyFactory object operates only on secret symmetric keys, whereas a java.

KeyFactory object processes the public and private key components of a key pair. Key factories are used to convert Key s opaque cryptographic keys of type java. Key into key specifications transparent representations of the underlying key material in a suitable format , and vice versa.

Objects of type java. Key , of which java. PublicKey , java. PrivateKey , and javax. SecretKey are subclasses, are opaque key objects, because you cannot tell how they are implemented. The underlying implementation is provider-dependent, and may be software or hardware based. Key factories allow providers to supply their own implementations of cryptographic keys. For example, if you have a key specification for a Diffie Hellman public key, consisting of the public value y , the prime modulus p , and the base g , and you feed the same specification to Diffie-Hellman key factories from different providers, the resulting PublicKey objects will most likely have different underlying implementations.

A provider should document the key specifications supported by its secret key factory. The following is an example of how to use a SecretKeyFactory to convert secret key data into a SecretKey object, which can be used for a subsequent Cipher operation:. In this case, the underlying implementation of SecretKey is based on the provider of KeyFactory. An alternative, provider-independent way of creating a functionally equivalent SecretKey object from the same key material is to use the javax.

SecretKeySpec class, which implements the javax. SecretKey interface:. If you have a key specification for a secret key, you can obtain an opaque SecretKey object from the specification by using the generateSecret method:. If you have a Secret Key object, you can get a corresponding key specification object by calling the getKeySpec method:.

The KeyPairGenerator class is an engine class used to generate pairs of public and private keys. There are two ways to generate a key pair: in an algorithm-independent manner, and in an algorithm-specific manner. The only difference between the two is the initialization of the object.

Please see the Examples section for examples of calls to the methods documented below. All key pair generation starts with a KeyPairGenerator. A key pair generator needs to be initialized before it can generate keys. In most cases, algorithm-independent initialization is sufficient. But in other cases, algorithm-specific initialization can be used.

All key pair generators share the concepts of a keysize and a source of randomness. The keysize is interpreted differently for different algorithms. For example, in the case of the DSA algorithm, the keysize corresponds to the length of the modulus. See the Standard Names document for information about the keysizes for specific algorithms.

Since no other parameters are specified when you call the above algorithm-independent initialize methods, it is up to the provider what to do about the algorithm-specific parameters if any to be associated with each of the keys. If the algorithm is a "DSA" algorithm, and the modulus size keysize is , , or , then the SUN provider uses a set of precomputed values for the p , q , and g parameters.

If the modulus size is not one of the above values, the SUN provider creates a new set of parameters. Other providers might have precomputed parameter sets for more than just the three modulus sizes mentioned above. Still others might not have a list of precomputed parameters at all and instead always create new parameter sets.

For situations where a set of algorithm-specific parameters already exists such as "community parameters" in DSA , there are two initialize methods that have an AlgorithmParameterSpec argument. One also has a SecureRandom argument, while the source of randomness is system-provided for the other:. The procedure for generating a key pair is always the same, regardless of initialization and of the algorithm. You always call the following method from KeyPairGenerator :.

A key generator for a particular symmetric-key algorithm creates a symmetric key that can be used with that algorithm. It also associates algorithm-specific parameters if any with the generated key. There are two ways to generate a key: in an algorithm-independent manner, and in an algorithm-specific manner. The only difference between the two is the initialization of the object:. All key generators share the concepts of a keysize and a source of randomness.

There is an init method that takes these two universally shared types of arguments. There is also one that takes just a keysize argument, and uses a system-provided source of randomness, and one that takes just a source of randomness:. Since no other parameters are specified when you call the above algorithm-independent init methods, it is up to the provider what to do about the algorithm-specific parameters if any to be associated with the generated key.

For situations where a set of algorithm-specific parameters already exists, there are two init methods that have an AlgorithmParameterSpec argument. In case the client does not explicitly initialize the KeyGenerator via a call to an init method , each provider must supply and document a default initialization.

Key agreement is a protocol by which 2 or more parties can establish the same cryptographic keys, without having to exchange any secret information. Each party initializes their key agreement object with their private key, and then enters the public keys for each party that will participate in the communication. In most cases, there are just two parties, but algorithms such as Diffie-Hellman allow for multiple parties 3 or more to participate.

When all the public keys have been entered, each KeyAgreement object will generate agree upon the same key. The KeyAgreement class provides the functionality of a key agreement protocol. The keys involved in establishing a shared secret are created by one of the key generators KeyPairGenerator or KeyGenerator , a KeyFactory , or as a result from an intermediate phase of the key agreement protocol.

Each party involved in the key agreement has to create a KeyAgreement object. KeyAgreement objects are obtained by using one of the KeyAgreement getInstance static factory methods. You initialize a KeyAgreement object with your private information. In the case of Diffie-Hellman, you initialize it with your Diffie-Hellman private key. Note that if the requested key agreement algorithm requires the specification of algorithm parameters, and only a key, but no parameters are provided to initialize the KeyAgreement object, the key must contain the required algorithm parameters.

For example, the Diffie-Hellman algorithm uses a prime modulus p and a base generator g as its parameters. Every key agreement protocol consists of a number of phases that need to be executed by each party involved in the key agreement.

The key parameter contains the key to be processed by that phase. In most cases, this is the public key of one of the other parties involved in the key agreement, or an intermediate key that was generated by a previous phase. The lastPhase parameter specifies whether or not the phase to be executed is the last one in the key agreement: A value of FALSE indicates that this is not the last phase of the key agreement there are more phases to follow , and a value of TRUE indicates that this is the last phase of the key agreement and the key agreement is completed, i.

After each party has executed all the required key agreement phases, it can compute the shared secret by calling one of the generateSecret methods:. The user keystore is by default stored in a file named. On Solaris systems "user. On Win32 systems, given user name uName , "user. These CA certificates can be used to help make trust decisions. Instead of using the system-wide cacerts keystore, applications can set up and use their own keystores, or even use the user keystore described above.

Currently, there are two command-line tools that make use of KeyStore : keytool and jarsigner , and also a GUI-based tool named policytool. It is also used by the Policy reference implementation when it processes policy files specifying the permissions allowed accesses to system resources to be granted to code from various sources. Since KeyStore is publicly available, JDK users can write additional security applications that use it. Applications can choose different types of keystore implementations from different providers, using the getInstance factory method in the KeyStore class.

A keystore type defines the storage and data format of the keystore information, and the algorithms used to protect private keys in the keystore and the integrity of the keystore itself. Keystore implementations of different types are not compatible.

The recommended keystore implementation is "pkcs12". Arbitrary attributes can be associated with individual entries in a PKCS12 keystore. The default keystore implementation type is "jks", which is specified in the following line in the java. To have tools and other applications use a different default keystore implementation, you can change that line to specify another default type.

For example, to use "pkcs12" as the default keystore implementation, change the line to:. Some applications, such as keytool , also let you override the default keystore type via the -storetype command-line parameter. The "jceks" implementation can parse and convert a "jks" keystore file to the "jceks" format.

You may upgrade your keystore of type "jks" to a keystore of type "jceks" by changing the password of a private-key entry in your keystore and specifying -storetype jceks as the keystore type. To apply the cryptographically strong er key protection supplied to a private key named "signkey" in your default keystore, use the following command, which will prompt you for the old and new key passwords:.

See Security Tools for more information about keytool and about keystores and how they are managed. Keystore implementations are provider-based. Developers interested in writing their own KeyStore implementations should consult How to Implement a Provider for the Java Cryptography Architecture for more information on this topic. The KeyStore class is an engine class that supplies well-defined interfaces to access and modify the information in a keystore.

This class represents an in-memory collection of keys and certificates. KeyStore manages two types of entries:. This type of keystore entry holds very sensitive cryptographic key information, which is stored in a protected format to prevent unauthorized access. Typically, a key stored in this type of entry is a secret key, or a private key accompanied by the certificate chain authenticating the corresponding public key.

Private keys and certificate chains are used by a given entity for self-authentication using digital signatures. This type of entry contains a single public key certificate belonging to another party. It is called a trusted certificate because the keystore owner trusts that the public key in the certificate indeed belongs to the identity identified by the subject owner of the certificate.

Whether keystores are persistent, and the mechanisms used by the keystore if it is persistent, are not specified here. This convention allows use of a variety of techniques for protecting sensitive e. Smart cards or other integrated cryptographic engines SafeKeyper are one option, and simpler mechanisms such as files may also be used in a variety of formats.

KeyStore objects are obtained by using one of the KeyStore getInstance static factory methods. To create an empty keystore, you pass null as the InputStream argument to the load method. All keystore entries are accessed via unique aliases.

The aliases method returns an enumeration of the alias names in the keystore:. A transparent representation of a set of parameters via AlgorithmParameterSpec means that you can access each parameter value in the set individually.

You can access these values through one of the get methods defined in the corresponding specification class e. In contrast, the AlgorithmParameters class supplies an opaque representation, in which you have no direct access to the parameter fields. You can only get the name of the algorithm associated with the parameter set via getAlgorithm and some kind of encoding for the parameter set via getEncoded. The algorithm parameter specification interfaces and classes in the java.

The following algorithm parameter specs are used specifically for digital signatures, as part of JSR AlgorithmParameters objects are obtained by using one of the AlgorithmParameters getInstance static factory methods. Once an AlgorithmParameters object is instantiated, it must be initialized via a call to init , using an appropriate parameter specification or parameter encoding:. A byte encoding of the parameters represented in an AlgorithmParameters object may be obtained via a call to getEncoded :.

A transparent parameter specification for the algorithm parameters may be obtained from an AlgorithmParameters object via a call to getParameterSpec :. AlgorithmParameterGenerator objects are obtained by using one of the AlgorithmParameterGenerator getInstance static factory methods.

The AlgorithmParameterGenerator object can be initialized in two different ways: an algorithm-independent manner or an algorithm-specific manner. The algorithm-independent approach uses the fact that all parameter generators share the concept of a "size" and a source of randomness. The measure of size is universally shared by all algorithm parameters, though it is interpreted differently for different algorithms.

For example, in the case of parameters for the DSA algorithm, "size" corresponds to the size of the prime modulus, in bits. See the Standard Names document for information about the sizes for specific algorithms. When using this approach, algorithm-specific parameter generation values--if any--default to some standard values.

One init method that takes these two universally shared types of arguments:. A third approach initializes a parameter generator object using algorithm-specific semantics, which are represented by a set of algorithm-specific parameter generation values supplied in an AlgorithmParameterSpec object:. A certificate factory for X. XCertificate , and CRLs that are an instance of java.

CertificateFactory objects are obtained by using one of the getInstance static factory methods. To generate a CertPath object and initialize it with data read from an input stream, use one of the following generateCertPath methods with or without specifying the encoding to be used for the data :.

This provider mainly provides a mapping from algorithm names to actual implementation classes. SSLContext s are initialized with two callback classes, KeyManager and TrustManager , which allow applications to first select authentication material to send and second to verify credentials sent by a peer. When a credential is needed, the KeyManager simply consults this KeyStore object and determines which credentials to present. This generator is then used to create a KeyPair which keytool would store along with the newly-created certificate in the KeyStore , which is eventually written to disk.

Internally, the CertPath implementation might create a Signature object, and use that to verify that the each of the signatures in the certificate chain. The client begins by sending a ClientHello message to the server. The server selects a ciphersuite to use, and sends that back in a ServerHello message, and begins creating JCA objects based on the suite selection.

This encrypted data is sent in a Client Key Exchange message. The server would use its corresponding PrivateKey to recover the bytes using a similar Cipher in decrypt mode. These bytes are then used to establish the actual encryption keys. The server sends its public key pieces in a ServerKeyExchange message protected by the DSA signature algorithm, and the client sends its public key in a ClientKeyExchange message. When the public keys are reassembled using another KeyFactory , they are fed into the agreement objects.

The KeyAgreement objects then generate agreed-upon bytes that are then used to establish the actual encryption keys. Once the actual encryption keys have been established, the secret key is used to initialize a symmetric Cipher object, and this cipher is used to protect all data in transit.

To help determine if the data has been modified, a MessageDigest is created and receives a copy of the data destined for the network. When the packet is complete, the digest hash is appended to data, and the entire packet is encrypted by the Cipher. If a block cipher such as AES is used, the data must be padded to make a complete block. On the remote side, the steps are simply reversed. Again, this is vastly simplified, but gives one an idea of how these classes might be combined to create a higher level protocol.

Note : This section should be ignored by most application developers. It is only for people whose applications may be exported to those few countries whose governments mandate cryptographic restrictions, if it is desired that such applications have fewer cryptographic restrictions than those mandated.

By default, an application can use cryptographic algorithms of any strength. The JCA framework includes an ability to enforce restrictions regarding the maximum strengths of cryptographic algorithms available to applications in different jurisdiction contexts locations. You specify these restrictions in jurisdiction policy files. It is possible that the governments of some or all such countries may allow certain applications to become exempt from some or all cryptographic restrictions.

For example, they may consider certain types of applications as "special" and thus exempt. Or they may exempt any application that utilizes an "exemption mechanism," such as key recovery. Applications deemed to be exempt could get access to stronger cryptography than that allowed for non-exempt applications in such countries. For an application to be recognized as "exempt" at runtime, it must meet the following conditions:. Below are sample steps required in order to make an application exempt from some cryptographic restrictions.

This is a basic outline that includes information about what is required by JCA in order to recognize and treat applications as being exempt. You will need to know the exemption requirements of the particular country or countries in which you would like your application to be able to be run but whose governments require cryptographic restrictions.

You will also need to know the requirements of a JCA framework vendor that has a process in place for handling exempt applications. Consult such a vendor for further information. When an application has a permission policy file associated with it in the same JAR file and that permission policy file specifies an exemption mechanism, then when the Cipher getInstance method is called to instantiate a Cipher , the JCA code searches the installed providers for one that implements the specified exemption mechanism.

After instantiating a Cipher , and prior to initializing it via a call to the Cipher init method , your code must call the following Cipher method:. This call returns the ExemptionMechanism object associated with the Cipher. You must then initialize the exemption mechanism implementation by calling the following method on the returned ExemptionMechanism :. The argument you supply should be the same as the argument of the same types that you will subsequently supply to a Cipher init method.

Once you have initialized the ExemptionMechanism , you can proceed as usual to initialize and use the Cipher. In order for an application to be recognized at runtime as being "exempt" from some or all cryptographic restrictions, it must have a permission policy file bundled with it in a JAR file.

The permission policy file specifies what cryptography-related permissions the application has, and under what conditions if any. The format of a permission entry in a permission policy file that accompanies an exempt application is the same as the format for a jurisdiction policy file downloaded with the JDK, which is:.

See Appendix B for more information about the jurisdiction policy file format. Some applications may be allowed to be completely unrestricted. Thus, the permission policy file that accompanies such an application usually just needs to contain the following:. If an application just uses a single algorithm or several specific algorithms , then the permission policy file could simply mention that algorithm or algorithms explicitly, rather than granting CryptoAllPermission.

It could just specify that there is no cryptographic restriction if the Blowfish algorithm is used. In order to do this, the permission policy file would look like the following:. If an application is considered "exempt" if an exemption mechanism is enforced, then the permission policy file that accompanies the application must specify one or more exemption mechanisms. At runtime, the application will be considered exempt if any of those exemption mechanisms is enforced.

Each exemption mechanism must be specified in a permission entry that looks like the following:. The list of possible exemption mechanism names includes:. As an example, suppose your application is exempt if either key recovery or key escrow is enforced. Then your permission policy file should contain the following:.

NOTE: Permission entries that specify exemption mechanisms should not also specify maximum key sizes. The allowed key sizes are actually determined from the installed exempt jurisdiction policy files, as described in the next section.

At runtime, when an application instantiates a Cipher via a call to its getInstance method and that application has an associated permission policy file, JCA checks to see whether the permission policy file has an entry that applies to the algorithm specified in the getInstance call. If it does, and the entry grants CryptoAllPermission or does not specify that an exemption mechanism must be enforced, it means there is no cryptographic restriction for this particular algorithm.

If the permission policy file has an entry that applies to the algorithm specified in the getInstance call and the entry does specify that an exemption mechanism must be enforced, then the exempt jurisdiction policy file s are examined. If the exempt permissions include an entry for the relevant algorithm and exemption mechanism, and that entry is implied by the permissions in the permission policy file bundled with the application, and if there is an implementation of the specified exemption mechanism available from one of the registered providers, then the maximum key size and algorithm parameter values for the Cipher are determined from the exempt permission entry.

If there is no exempt permission entry implied by the relevant entry in the permission policy file bundled with the application, or if there is no implementation of the specified exemption mechanism available from any of the registered providers, then the application is only allowed the standard default cryptographic permissions. Here are some short examples which illustrate use of several of the JCA mechanisms.

In addition, complete working examples can be found in Appendix D. First create the message digest object, as in the following example:. Next, suppose we have three byte arrays, i1 , i2 and i3 , which form the total input whose message digest we want to compute. This digest or "hash" could be calculated via the following calls:.

Some hash implementations may support intermediate hashes through cloning. Suppose we want to calculate separate hashes for:. In this example we will generate a public-private key pair for the algorithm named "DSA" Digital Signature Algorithm , and use this keypair in future examples. We will generate keys with a bit modulus. The KeyPairGenerator class initialization methods at a minimum needs a keysize. If the source of randomness is not explicitly provided, a SecureRandom implementation of the highest-priority installed provider will be used.

Thus to generate keys with a keysize of , simply call:. Suppose your key pair generator is for the "DSA" algorithm, and you have a set of DSA-specific parameters, p , q , and g , that you would like to use to generate your key pair. The following signature generation and verification examples use the KeyPair generated in the key pair example above. Further suppose you want to use your private key to digitally sign some data, which is in a byte array named someData.

You would do the following steps, which also illustrate creating a key specification and using a key factory to obtain a PrivateKey from the key specification initSign requires a PrivateKey :. For the public key, assume, as in the signing example above, you have the components of the DSA public key corresponding to the DSA private key used to sign the data. Now, assume Alice has received these files, and she copied the data bytes from the data file to a byte array named data , the signature bytes from the signature file to a byte array named signature , and the encoded public key bytes from the public key file to a byte array named encodedPubKey.

Alice can now execute the following code to verify the signature. The code also illustrates how to use a key factory in order to instantiate a DSA public key from its encoding initVerify requires a PublicKey. In many cases you would like to know if two keys are equal; however, the default method java.

The most provider-independent approach is to compare the encoded keys. The following code demonstrates this idea:. The following example reads a file with Baseencoded certificates, which are each bounded at the beginning by. The following example parses a PKCS7-formatted certificate reply stored in a file and extracts all the certificates from it:. This section takes the user through the process of generating a key, creating and initializing a cipher object, encrypting a file, and then decrypting it.

We do not specify a provider, because we do not care about a particular AES key generation implementation. Since we do not initialize the KeyGenerator, a system-provided source of randomness and a default keysize will be used to create the AES key:. After the key has been generated, the same KeyGenerator object can be re-used to create further keys.

The next step is to create a Cipher instance. To do this, we use one of the getInstance factory methods of the Cipher class. We do not specify a provider, because we do not care about a particular implementation of the requested transformation.

We use the generated aesKey from above to initialize the Cipher object for encryption:. It would seem logical to collect and store the password in an object of type java. This feature makes String objects unsuitable for storing security sensitive information such as user passwords. You should always collect and store security sensitive information in a char array instead. For that reason, the javax. PBEKeySpec class takes and returns a password as a char array. See the ReadPassword class in the sample code in Appendix D for one possible way of reading character array passwords from an input stream.

The same salt and iteration count that are used for encryption must be used for decryption:. Please refer to Appendix D for sample programs exercising the Diffie-Hellman key exchange between 2 and 3 parties. This document also contains more information about the algorithm specifications. Specific provider information can be found in the Sun Provider Documentation.

Java crypto вывод биткоин на приват24

Java Encryption and Decryption Tutorial (Basic)

Следующая статья курс обмена валюты в казахстане

Другие материалы по теме

  • Обмен валют рублей в евро
  • Биткоин китай запретил
  • Обмен валют в банках новосибирск
  • Обмен валют алматы на сегодня
  • Комментарии

    Добавить комментарий

    Ваш e-mail не будет опубликован. Обязательные поля помечены *