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.jce.interfaces;

import java.security.Key;
import java.security.PrivateKey;
import java.security.PublicKey;


key pair for use with an integrated encryptor

/**
 * key pair for use with an integrated encryptor
 */
public interface IESKey
    extends Key
{
    
return the intended recipient's/sender's public key.

/**
     * return the intended recipient's/sender's public key.
     */
    public PublicKey getPublic();

    
return the local private key.

/**
     * return the local private key.
     */
    public PrivateKey getPrivate();
}