gnu.crypto.key.dh
Class DiffieHellmanKeyAgreement

java.lang.Object
  gnu.crypto.key.BaseKeyAgreementParty
      gnu.crypto.key.dh.DiffieHellmanKeyAgreement

All Implemented Interfaces:

IKeyAgreementParty

Direct Known Subclasses:

DiffieHellmanReceiver, DiffieHellmanSender

public abstract class DiffieHellmanKeyAgreement

extends BaseKeyAgreementParty

The basic version of the Diffie-Hellman key agreement is described in the Handbook of Applied Cryptography [HAC] as follows:

• An appropriate prime p and generator g of Z_p^* (2 <= g <= p-2) are selected and published.
• A and B each send the other one message over an open channel; as a result, they both can then compute a shared secret key K which they can use to protect their future communication.
• A chooses a random secret x, 1 <= x <= p-2, and sends B message (1) which is g^x mod p.
• B chooses a random secret y, 1 <= y <= p-2, and sends A message (2) which is g^y mod p.
• B receives message (1) and computes the shared key as K = (g^x)^y mod p.
• A receives message (2) and computes the shared key as K = (g^y)^x mod p.

RFC-2631 describes a Static-Static Mode of operations with Diffie-Hellman keypairs as follows:

 "In Static-Static mode, both the sender and the recipient have a
   static (and certified) key pair. Since the sender's and recipient's
   keys are therefore the same for each message, ZZ will be the same for
   each message. Thus, partyAInfo MUST be used (and different for each
   message) in order to ensure that different messages use different
   KEKs. Implementations MAY implement Static-Static mode."
 

Reference:

1. Diffie-Hellman Key Agreement Method
   Eric Rescorla.
2. [HAC]: Handbook of Applied Cryptography.
   CRC Press, Inc. ISBN 0-8493-8523-7, 1997
   Menezes, A., van Oorschot, P. and S. Vanstone.

Version:

$Revision: 1.2 $

Field Summary

static java.lang.String	KA_DIFFIE_HELLMAN_OWNER_PRIVATE_KEY
protected javax.crypto.interfaces.DHPrivateKey	ownerKey The key agreement party's private key.
static java.lang.String	SOURCE_OF_RANDOMNESS
protected java.math.BigInteger	ZZ The shared secret key.

Fields inherited from class gnu.crypto.key.BaseKeyAgreementParty

complete, initialised, name, rnd, step, TWO

Constructor Summary

protected

DiffieHellmanKeyAgreement()

Method Summary

protected void	engineReset()
protected byte[]	engineSharedSecret()

Methods inherited from class gnu.crypto.key.BaseKeyAgreementParty

engineInit, engineProcessMessage, getSharedSecret, init, isComplete, name, nextRandomBytes, processMessage, reset

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

SOURCE_OF_RANDOMNESS

public static final java.lang.String SOURCE_OF_RANDOMNESS

See Also:

Constant Field Values

KA_DIFFIE_HELLMAN_OWNER_PRIVATE_KEY

public static final java.lang.String KA_DIFFIE_HELLMAN_OWNER_PRIVATE_KEY

See Also:

Constant Field Values

ownerKey

protected javax.crypto.interfaces.DHPrivateKey ownerKey

The key agreement party's private key.

ZZ

protected java.math.BigInteger ZZ

The shared secret key.

Constructor Detail

DiffieHellmanKeyAgreement

protected DiffieHellmanKeyAgreement()

Method Detail

engineSharedSecret

protected byte[] engineSharedSecret()
                             throws KeyAgreementException

Specified by:

engineSharedSecret in class BaseKeyAgreementParty

Throws:

KeyAgreementException

engineReset

protected void engineReset()

Specified by:

engineReset in class BaseKeyAgreementParty