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`java.lang.Object`

`gnu.javax.crypto.key.BaseKeyAgreementParty`

`gnu.javax.crypto.key.dh.DiffieHellmanKeyAgreement`

**Implemented Interfaces:**- IKeyAgreementParty

**Known Direct 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:

- Diffie-Hellman Key
Agreement Method

Eric Rescorla. - [HAC]: Handbook of
Applied Cryptography.

CRC Press, Inc. ISBN 0-8493-8523-7, 1997

Menezes, A., van Oorschot, P. and S. Vanstone.

## Field Summary

`static String`

`static String`

`protected BigInteger`

`ZZ`

- The shared secret key.

`protected DHPrivateKey`

`ownerKey`

- The key agreement party's private key.

### Fields inherited from class gnu.javax.crypto.key.BaseKeyAgreementParty

`TWO`

,`complete`

,`initialised`

,`irnd`

,`name`

,`rnd`

,`step`

## Constructor Summary

## Method Summary

`protected void`

`protected byte[]`

### Methods inherited from class gnu.javax.crypto.key.BaseKeyAgreementParty

`engineInit`

,`engineProcessMessage`

,`engineReset`

,`engineSharedSecret`

,`getSharedSecret`

,`init`

,`isComplete`

,`name`

,`nextRandomBytes`

,`processMessage`

,`reset`

### Methods inherited from class java.lang.Object

`clone`

,`equals`

,`extends Object> getClass`

,`finalize`

,`hashCode`

,`notify`

,`notifyAll`

,`toString`

,`wait`

,`wait`

,`wait`

public static final String KA_DIFFIE_HELLMAN_OWNER_PRIVATE_KEY

Field Value:- "gnu.crypto.dh.ka.owner.private.key"

public static final String SOURCE_OF_RANDOMNESS

Field Value:- "gnu.crypto.dh.ka.prng"

protected byte[] engineSharedSecret() throws KeyAgreementException

Overrides:- engineSharedSecret in interface BaseKeyAgreementParty

DiffieHellmanKeyAgreement.java --
Copyright (C) 2003, 2006 Free Software Foundation, Inc.
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