http://www.bouncycastle.org/java.html: 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. 
package org.bouncycastle.crypto.tls;

import java.io.IOException;

import org.bouncycastle.crypto.params.AsymmetricKeyParameter;

public interface TlsAgreementCredentials extends TlsCredentials
{
    byte[] generateAgreement(AsymmetricKeyParameter serverPublicKey) throws IOException;
}