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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.
package org.bouncycastle.crypto.agreement;
import java.math.BigInteger;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.params.ECDHUPrivateParameters;
import org.bouncycastle.crypto.params.ECDHUPublicParameters;
import org.bouncycastle.util.Arrays;
import org.bouncycastle.util.BigIntegers;
/**
* EC Unified static/ephemeral agreement as described in NIST SP 800-56A using EC co-factor Diffie-Hellman.
*/
public class ECDHCUnifiedAgreement
{
private ECDHUPrivateParameters privParams;
public void init(
CipherParameters key)
{
this.privParams = (ECDHUPrivateParameters)key;
}
public int getFieldSize()
{
return (privParams.getStaticPrivateKey().getParameters().getCurve().getFieldSize() + 7) / 8;
}
public byte[] calculateAgreement(CipherParameters pubKey)
{
ECDHUPublicParameters pubParams = (ECDHUPublicParameters)pubKey;
ECDHCBasicAgreement sAgree = new ECDHCBasicAgreement();
ECDHCBasicAgreement eAgree = new ECDHCBasicAgreement();
sAgree.init(privParams.getStaticPrivateKey());
BigInteger sComp = sAgree.calculateAgreement(pubParams.getStaticPublicKey());
eAgree.init(privParams.getEphemeralPrivateKey());
BigInteger eComp = eAgree.calculateAgreement(pubParams.getEphemeralPublicKey());
return Arrays.concatenate(
BigIntegers.asUnsignedByteArray(this.getFieldSize(), eComp),
BigIntegers.asUnsignedByteArray(this.getFieldSize(), sComp));
}
}
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