java.lang.Object
- javax.crypto.KeyAgreement

```
public class KeyAgreement
extends Object
```
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:
- DiffieHellman
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.
Since:

1.4

See Also:
KeyGenerator, SecretKey

Constructor Summary

Constructors
Modifier	Constructor and Description
`protected`	`KeyAgreement(KeyAgreementSpi keyAgreeSpi, Provider provider, String algorithm)` Creates a KeyAgreement object.

Method Summary

Methods
Modifier and Type	Method and Description
`Key`	`doPhase(Key key, boolean lastPhase)` 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.
`byte[]`	`generateSecret()` Generates the shared secret and returns it in a new buffer.
`int`	`generateSecret(byte[] sharedSecret, int offset)` Generates the shared secret, and places it into the buffer `sharedSecret`, beginning at `offset` inclusive.
`SecretKey`	`generateSecret(String algorithm)` Creates the shared secret and returns it as a `SecretKey` object of the specified algorithm.
`String`	`getAlgorithm()` Returns the algorithm name of this `KeyAgreement` object.
`static KeyAgreement`	`getInstance(String algorithm)` Returns a `KeyAgreement` object that implements the specified key agreement algorithm.
`static KeyAgreement`	`getInstance(String algorithm, Provider provider)` Returns a `KeyAgreement` object that implements the specified key agreement algorithm.
`static KeyAgreement`	`getInstance(String algorithm, String provider)` Returns a `KeyAgreement` object that implements the specified key agreement algorithm.
`Provider`	`getProvider()` Returns the provider of this `KeyAgreement` object.
`void`	`init(Key key)` Initializes this key agreement with the given key, which is required to contain all the algorithm parameters required for this key agreement.
`void`	`init(Key key, AlgorithmParameterSpec params)` Initializes this key agreement with the given key and set of algorithm parameters.
`void`	`init(Key key, AlgorithmParameterSpec params, SecureRandom random)` Initializes this key agreement with the given key, set of algorithm parameters, and source of randomness.
`void`	`init(Key key, SecureRandom random)` Initializes this key agreement with the given key and source of randomness.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - KeyAgreement
```
protected KeyAgreement(KeyAgreementSpi keyAgreeSpi,
            Provider provider,
            String algorithm)
```
    Creates a KeyAgreement object.
    
    Parameters:
    keyAgreeSpi - the delegate
    provider - the provider
    algorithm - the algorithm
- Method Detail
  - getAlgorithm
```
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.
    
    Returns:
    the algorithm name of this KeyAgreement object.
  - getInstance
```
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.
    
    Parameters:
    algorithm - the standard name of the requested key agreement algorithm. See the KeyAgreement section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
    
    Returns:
    the new KeyAgreement object.
    
    Throws:
    
    NullPointerException - if the specified algorithm is null.
    
    NoSuchAlgorithmException - if no Provider supports a KeyAgreementSpi implementation for the specified algorithm.
    See Also:
    Provider
  - getInstance
```
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.
    
    Parameters:
    algorithm - the standard name of the requested key agreement algorithm. See the KeyAgreement section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
    provider - the name of the provider.
    
    Returns:
    the new KeyAgreement object.
    
    Throws:
    
    NullPointerException - if the specified algorithm is null.
    
    NoSuchAlgorithmException - if a KeyAgreementSpi implementation for the specified algorithm is not available from the specified provider.
    
    NoSuchProviderException - if the specified provider is not registered in the security provider list.
    
    IllegalArgumentException - if the provider is null or empty.
    See Also:
    Provider
  - getInstance
```
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.
    
    Parameters:
    algorithm - the standard name of the requested key agreement algorithm. See the KeyAgreement section in the Java Cryptography Architecture Standard Algorithm Name Documentation for information about standard algorithm names.
    provider - the provider.
    
    Returns:
    the new KeyAgreement object.
    
    Throws:
    
    NullPointerException - if the specified algorithm is null.
    
    NoSuchAlgorithmException - if a KeyAgreementSpi implementation for the specified algorithm is not available from the specified Provider object.
    
    IllegalArgumentException - if the provider is null.
    See Also:
    Provider
  - getProvider
```
public final Provider getProvider()
```
    Returns the provider of this KeyAgreement object.
    
    Returns:
    the provider of this KeyAgreement object
  - init
```
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.)
    
    Parameters:
    key - the party's private information. For example, in the case of the Diffie-Hellman key agreement, this would be the party's own Diffie-Hellman private key.
    
    Throws:
    
    InvalidKeyException - if the given key is inappropriate for this key agreement, e.g., is of the wrong type or has an incompatible algorithm type.
  - init
```
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.
    
    Parameters:
    key - the party's private information. For example, in the case of the Diffie-Hellman key agreement, this would be the party's own Diffie-Hellman private key.
    random - the source of randomness
    
    Throws:
    
    InvalidKeyException - if the given key is inappropriate for this key agreement, e.g., is of the wrong type or has an incompatible algorithm type.
  - init
```
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.)
    
    Parameters:
    key - the party's private information. For example, in the case of the Diffie-Hellman key agreement, this would be the party's own Diffie-Hellman private key.
    params - the key agreement parameters
    
    Throws:
    
    InvalidKeyException - if the given key is inappropriate for this key agreement, e.g., is of the wrong type or has an incompatible algorithm type.
    
    InvalidAlgorithmParameterException - if the given parameters are inappropriate for this key agreement.
  - init
```
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.
    
    Parameters:
    key - the party's private information. For example, in the case of the Diffie-Hellman key agreement, this would be the party's own Diffie-Hellman private key.
    params - the key agreement parameters
    random - the source of randomness
    
    Throws:
    
    InvalidKeyException - if the given key is inappropriate for this key agreement, e.g., is of the wrong type or has an incompatible algorithm type.
    
    InvalidAlgorithmParameterException - if the given parameters are inappropriate for this key agreement.
  - doPhase
```
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.
    
    Parameters:
    key - the key for this phase. For example, in the case of Diffie-Hellman between 2 parties, this would be the other party's Diffie-Hellman public key.
    lastPhase - flag which indicates whether or not this is the last phase of this key agreement.
    
    Returns:
    the (intermediate) key resulting from this phase, or null if this phase does not yield a key
    
    Throws:
    
    InvalidKeyException - if the given key is inappropriate for this phase.
    
    IllegalStateException - if this key agreement has not been initialized.
  - generateSecret
```
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.
    
    Returns:
    the new buffer with the shared secret
    
    Throws:
    
    IllegalStateException - if this key agreement has not been completed yet
  - generateSecret
```
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.
    
    Parameters:
    sharedSecret - the buffer for the shared secret
    offset - the offset in sharedSecret where the shared secret will be stored
    
    Returns:
    the number of bytes placed into sharedSecret
    
    Throws:
    
    IllegalStateException - if this key agreement has not been completed yet
    
    ShortBufferException - if the given output buffer is too small to hold the secret
  - generateSecret
```
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.
    
    Parameters:
    algorithm - the requested secret-key algorithm
    
    Returns:
    the shared secret key
    
    Throws:
    
    IllegalStateException - if this key agreement has not been completed yet
    
    NoSuchAlgorithmException - if the specified secret-key algorithm is not available
    
    InvalidKeyException - if the shared secret-key material cannot be used to generate a secret key of the specified algorithm (e.g., the key material is too short)

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Document créé le 29/08/2006, dernière modification le 04/03/2020
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Références

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Table des matières Haut

Class KeyAgreement

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

KeyAgreement

Method Detail

getAlgorithm

getInstance

getInstance

getInstance

getProvider

init

init

init

init

doPhase

generateSecret

generateSecret

generateSecret

Références