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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8 with debug enabled.
package org.bouncycastle.jcajce.provider.asymmetric.dh;
import java.math.BigInteger;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.Key;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.AlgorithmParameterSpec;
import javax.crypto.SecretKey;
import javax.crypto.ShortBufferException;
import javax.crypto.interfaces.DHPrivateKey;
import javax.crypto.interfaces.DHPublicKey;
import javax.crypto.spec.DHParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import org.bouncycastle.crypto.DerivationFunction;
import org.bouncycastle.crypto.agreement.kdf.DHKEKGenerator;
import org.bouncycastle.crypto.util.DigestFactory;
import org.bouncycastle.jcajce.provider.asymmetric.util.BaseAgreementSpi;
import org.bouncycastle.jcajce.spec.UserKeyingMaterialSpec;
/**
* Diffie-Hellman key agreement. There's actually a better way of doing this
* if you are using long term public keys, see the light-weight version for
* details.
*/
public class KeyAgreementSpi
extends BaseAgreementSpi
{
private static final BigInteger ONE = BigInteger.valueOf(1);
private static final BigInteger TWO = BigInteger.valueOf(2);
private BigInteger x;
private BigInteger p;
private BigInteger g;
private BigInteger result;
public KeyAgreementSpi()
{
super("Diffie-Hellman", null);
}
public KeyAgreementSpi(
String kaAlgorithm,
DerivationFunction kdf)
{
super(kaAlgorithm, kdf);
}
protected byte[] bigIntToBytes(
BigInteger r)
{
//
// RFC 2631 (2.1.2) specifies that the secret should be padded with leading zeros if necessary
// must be the same length as p
//
int expectedLength = (p.bitLength() + 7) / 8;
byte[] tmp = r.toByteArray();
if (tmp.length == expectedLength)
{
return tmp;
}
if (tmp[0] == 0 && tmp.length == expectedLength + 1)
{
byte[] rv = new byte[tmp.length - 1];
System.arraycopy(tmp, 1, rv, 0, rv.length);
return rv;
}
// tmp must be shorter than expectedLength
// pad to the left with zeros.
byte[] rv = new byte[expectedLength];
System.arraycopy(tmp, 0, rv, rv.length - tmp.length, tmp.length);
return rv;
}
protected Key engineDoPhase(
Key key,
boolean lastPhase)
throws InvalidKeyException, IllegalStateException
{
if (x == null)
{
throw new IllegalStateException("Diffie-Hellman not initialised.");
}
if (!(key instanceof DHPublicKey))
{
throw new InvalidKeyException("DHKeyAgreement doPhase requires DHPublicKey");
}
DHPublicKey pubKey = (DHPublicKey)key;
if (!pubKey.getParams().getG().equals(g) || !pubKey.getParams().getP().equals(p))
{
throw new InvalidKeyException("DHPublicKey not for this KeyAgreement!");
}
BigInteger peerY = ((DHPublicKey)key).getY();
if (peerY == null || peerY.compareTo(TWO) < 0
|| peerY.compareTo(p.subtract(ONE)) >= 0)
{
throw new InvalidKeyException("Invalid DH PublicKey");
}
result = peerY.modPow(x, p);
if (result.compareTo(ONE) == 0)
{
throw new InvalidKeyException("Shared key can't be 1");
}
if (lastPhase)
{
return null;
}
return new BCDHPublicKey(result, pubKey.getParams());
}
protected byte[] engineGenerateSecret()
throws IllegalStateException
{
if (x == null)
{
throw new IllegalStateException("Diffie-Hellman not initialised.");
}
return super.engineGenerateSecret();
}
protected int engineGenerateSecret(
byte[] sharedSecret,
int offset)
throws IllegalStateException, ShortBufferException
{
if (x == null)
{
throw new IllegalStateException("Diffie-Hellman not initialised.");
}
return super.engineGenerateSecret(sharedSecret, offset);
}
protected SecretKey engineGenerateSecret(
String algorithm)
throws NoSuchAlgorithmException
{
if (x == null)
{
throw new IllegalStateException("Diffie-Hellman not initialised.");
}
byte[] res = bigIntToBytes(result);
// for JSSE compatibility
if (algorithm.equals("TlsPremasterSecret"))
{
return new SecretKeySpec(trimZeroes(res), algorithm);
}
return super.engineGenerateSecret(algorithm);
}
protected void engineInit(
Key key,
AlgorithmParameterSpec params,
SecureRandom random)
throws InvalidKeyException, InvalidAlgorithmParameterException
{
if (!(key instanceof DHPrivateKey))
{
throw new InvalidKeyException("DHKeyAgreement requires DHPrivateKey for initialisation");
}
DHPrivateKey privKey = (DHPrivateKey)key;
if (params != null)
{
if (params instanceof DHParameterSpec) // p, g override.
{
DHParameterSpec p = (DHParameterSpec)params;
this.p = p.getP();
this.g = p.getG();
}
else if (params instanceof UserKeyingMaterialSpec)
{
this.p = privKey.getParams().getP();
this.g = privKey.getParams().getG();
this.ukmParameters = ((UserKeyingMaterialSpec)params).getUserKeyingMaterial();
}
else
{
throw new InvalidAlgorithmParameterException("DHKeyAgreement only accepts DHParameterSpec");
}
}
else
{
this.p = privKey.getParams().getP();
this.g = privKey.getParams().getG();
}
this.x = this.result = privKey.getX();
}
protected void engineInit(
Key key,
SecureRandom random)
throws InvalidKeyException
{
if (!(key instanceof DHPrivateKey))
{
throw new InvalidKeyException("DHKeyAgreement requires DHPrivateKey");
}
DHPrivateKey privKey = (DHPrivateKey)key;
this.p = privKey.getParams().getP();
this.g = privKey.getParams().getG();
this.x = this.result = privKey.getX();
}
protected byte[] calcSecret()
{
return bigIntToBytes(result);
}
public static class DHwithRFC2631KDF
extends KeyAgreementSpi
{
public DHwithRFC2631KDF()
{
super("DHwithRFC2631KDF", new DHKEKGenerator(DigestFactory.createSHA1()));
}
}
}
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