public final class

DHKeyAgreement

extends KeyAgreementSpi
java.lang.Object
   ↳ javax.crypto.KeyAgreementSpi
     ↳ com.sun.crypto.provider.DHKeyAgreement

Class Overview

This class implements the Diffie-Hellman key agreement protocol between any number of parties.

Summary

Public Constructors
DHKeyAgreement()
Verify the SunJCE provider in the constructor.
Protected Methods
Key engineDoPhase(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.
int engineGenerateSecret(byte[] sharedSecret, int offset)
Generates the shared secret, and places it into the buffer sharedSecret, beginning at offset.
byte[] engineGenerateSecret()
Generates the shared secret and returns it in a new buffer.
SecretKey engineGenerateSecret(String algorithm)
Creates the shared secret and returns it as a secret key object of the requested algorithm type.
void engineInit(Key key, SecureRandom random)
Initializes this key agreement with the given key and source of randomness.
void engineInit(Key key, AlgorithmParameterSpec params, SecureRandom random)
Initializes this key agreement with the given key, set of algorithm parameters, and source of randomness.
[Expand]
Inherited Methods
From class javax.crypto.KeyAgreementSpi
From class java.lang.Object

Public Constructors

public DHKeyAgreement ()

Verify the SunJCE provider in the constructor.

Throws
SecurityException if fails to verify its own integrity

Protected Methods

protected Key engineDoPhase (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.

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.

protected int engineGenerateSecret (byte[] sharedSecret, int offset)

Generates the shared secret, and places it into the buffer sharedSecret, beginning at offset.

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 KeyAgreementSpi object, so that it can be reused for further key agreements. Unless this key agreement is reinitialized with one of the engineInit 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

protected byte[] engineGenerateSecret ()

Generates the shared secret and returns it in a new buffer.

This method resets this KeyAgreementSpi object, so that it can be reused for further key agreements. Unless this key agreement is reinitialized with one of the engineInit 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

protected SecretKey engineGenerateSecret (String algorithm)

Creates the shared secret and returns it as a secret key object of the requested algorithm type.

This method resets this KeyAgreementSpi object, so that it can be reused for further key agreements. Unless this key agreement is reinitialized with one of the engineInit 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 requested secret key algorithm is not available
InvalidKeyException if the shared secret key material cannot be used to generate a secret key of the requested algorithm type (e.g., the key material is too short)

protected void engineInit (Key key, SecureRandom random)

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.

protected void engineInit (Key key, AlgorithmParameterSpec params, SecureRandom random)

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.