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javax.crypto
public class: KeyAgreement [javadoc | source]
java.lang.Object
   javax.crypto.KeyAgreement
This class provides the functionality of a key agreement (or key exchange) 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.

For each of the correspondents in the key exchange, doPhase needs to be called. For example, if this key exchange is with one other party, doPhase needs to be called once, with the lastPhase flag set to true. If this key exchange is with two other parties, doPhase needs to be called twice, the first time setting the lastPhase flag to false, and the second time setting it to true. There may be any number of parties involved in a key exchange.

Every implementation of the Java platform is required to support the following standard KeyAgreement algorithm:

This algorithm is described in the KeyAgreement section of the Java Cryptography Architecture Standard Algorithm Name Documentation. Consult the release documentation for your implementation to see if any other algorithms are supported.
Constructor:
 protected KeyAgreement(KeyAgreementSpi keyAgreeSpi,
    Provider provider,
    String algorithm) 
    Creates a KeyAgreement object.
    Parameters:
    keyAgreeSpi - the delegate
    provider - the provider
    algorithm - the algorithm
Method from javax.crypto.KeyAgreement Summary:
chooseFirstProvider,   doPhase,   generateSecret,   generateSecret,   generateSecret,   getAlgorithm,   getInstance,   getInstance,   getInstance,   getProvider,   init,   init,   init,   init
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from javax.crypto.KeyAgreement Detail:
  void chooseFirstProvider() 
    Choose the Spi from the first provider available. Used if delayed provider selection is not possible because init() is not the first method called.
 public final Key doPhase(Key key,
    boolean lastPhase) throws InvalidKeyException, IllegalStateException 
    Executes the next phase of this key agreement with the given key that was received from one of the other parties involved in this key agreement.
 public final byte[] generateSecret() throws IllegalStateException 
    Generates the shared secret and returns it in a new buffer.

    This method resets this KeyAgreement object, so that it can be reused for further key agreements. Unless this key agreement is reinitialized with one of the init methods, the same private information and algorithm parameters will be used for subsequent key agreements.

 public final SecretKey generateSecret(String algorithm) throws IllegalStateException, NoSuchAlgorithmException, InvalidKeyException 
    Creates the shared secret and returns it as a SecretKey object of the specified algorithm.

    This method resets this KeyAgreement object, so that it can be reused for further key agreements. Unless this key agreement is reinitialized with one of the init methods, the same private information and algorithm parameters will be used for subsequent key agreements.

 public final int generateSecret(byte[] sharedSecret,
    int offset) throws IllegalStateException, ShortBufferException 
    Generates the shared secret, and places it into the buffer sharedSecret, beginning at offset inclusive.

    If the sharedSecret buffer is too small to hold the result, a ShortBufferException is thrown. In this case, this call should be repeated with a larger output buffer.

    This method resets this KeyAgreement object, so that it can be reused for further key agreements. Unless this key agreement is reinitialized with one of the init methods, the same private information and algorithm parameters will be used for subsequent key agreements.

 public final String getAlgorithm() 
    Returns the algorithm name of this KeyAgreement object.

    This is the same name that was specified in one of the getInstance calls that created this KeyAgreement object.

 public static final KeyAgreement getInstance(String algorithm) throws NoSuchAlgorithmException 
    Returns a KeyAgreement object that implements the specified key agreement algorithm.

    This method traverses the list of registered security Providers, starting with the most preferred Provider. A new KeyAgreement object encapsulating the KeyAgreementSpi implementation from the first Provider that supports the specified algorithm is returned.

    Note that the list of registered providers may be retrieved via the Security.getProviders() method.

 public static final KeyAgreement getInstance(String algorithm,
    String provider) throws NoSuchAlgorithmException, NoSuchProviderException 
    Returns a KeyAgreement object that implements the specified key agreement algorithm.

    A new KeyAgreement object encapsulating the KeyAgreementSpi implementation from the specified provider is returned. The specified provider must be registered in the security provider list.

    Note that the list of registered providers may be retrieved via the Security.getProviders() method.

 public static final KeyAgreement getInstance(String algorithm,
    Provider provider) throws NoSuchAlgorithmException 
    Returns a KeyAgreement object that implements the specified key agreement algorithm.

    A new KeyAgreement object encapsulating the KeyAgreementSpi implementation from the specified Provider object is returned. Note that the specified Provider object does not have to be registered in the provider list.

 public final Provider getProvider() 
    Returns the provider of this KeyAgreement object.
 public final  void init(Key key) throws InvalidKeyException 
    Initializes this key agreement with the given key, which is required to contain all the algorithm parameters required for this key agreement.

    If this key agreement requires any random bytes, it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)

 public final  void init(Key key,
    SecureRandom random) throws InvalidKeyException 
    Initializes this key agreement with the given key and source of randomness. The given key is required to contain all the algorithm parameters required for this key agreement.

    If the key agreement algorithm requires random bytes, it gets them from the given source of randomness, random. However, if the underlying algorithm implementation does not require any random bytes, random is ignored.

 public final  void init(Key key,
    AlgorithmParameterSpec params) throws InvalidKeyException, InvalidAlgorithmParameterException 
    Initializes this key agreement with the given key and set of algorithm parameters.

    If this key agreement requires any random bytes, it will get them using the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness will be used.)

 public final  void init(Key key,
    AlgorithmParameterSpec params,
    SecureRandom random) throws InvalidKeyException, InvalidAlgorithmParameterException 
    Initializes this key agreement with the given key, set of algorithm parameters, and source of randomness.