org.bouncycastle.crypto.agreement
public class: DHAgreement [javadoc |
source]
java.lang.Object
org.bouncycastle.crypto.agreement.DHAgreement
a Diffie-Hellman key exchange engine.
note: This uses MTI/A0 key agreement in order to make the key agreement
secure against passive attacks. If you're doing Diffie-Hellman and both
parties have long term public keys you should look at using this. For
further information have a look at RFC 2631.
It's possible to extend this to more than two parties as well, for the moment
that is left as an exercise for the reader.
| Method from org.bouncycastle.crypto.agreement.DHAgreement Detail: |
|---|
 public BigInteger calculateAgreement(DHPublicKeyParameters pub,
BigInteger message) {
if (!pub.getParameters().equals(dhParams))
{
throw new IllegalArgumentException("Diffie-Hellman public key has wrong parameters.");
}
BigInteger p = dhParams.getP();
return message.modPow(key.getX(), p).multiply(pub.getY().modPow(privateValue, p)).mod(p);
}
given a message from a given party and the corresponding public key,
calculate the next message in the agreement sequence. In this case
this will represent the shared secret. |
public BigInteger calculateMessage() {
DHKeyPairGenerator dhGen = new DHKeyPairGenerator();
dhGen.init(new DHKeyGenerationParameters(random, dhParams));
AsymmetricCipherKeyPair dhPair = dhGen.generateKeyPair();
this.privateValue = ((DHPrivateKeyParameters)dhPair.getPrivate()).getX();
return ((DHPublicKeyParameters)dhPair.getPublic()).getY();
} calculate our initial message. |
public void init(CipherParameters param) {
AsymmetricKeyParameter kParam;
if (param instanceof ParametersWithRandom)
{
ParametersWithRandom rParam = (ParametersWithRandom)param;
this.random = rParam.getRandom();
kParam = (AsymmetricKeyParameter)rParam.getParameters();
}
else
{
this.random = new SecureRandom();
kParam = (AsymmetricKeyParameter)param;
}
if (!(kParam instanceof DHPrivateKeyParameters))
{
throw new IllegalArgumentException("DHEngine expects DHPrivateKeyParameters");
}
this.key = (DHPrivateKeyParameters)kParam;
this.dhParams = key.getParameters();
} |
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