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 to JDK 1.8.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.crypto;

public class EphemeralKeyPair
{
    private AsymmetricCipherKeyPair keyPair;
    private KeyEncoder publicKeyEncoder;

    public EphemeralKeyPair(AsymmetricCipherKeyPair keyPair, KeyEncoder publicKeyEncoder)
    {
        this.keyPair = keyPair;
        this.publicKeyEncoder = publicKeyEncoder;
    }

    public AsymmetricCipherKeyPair getKeyPair()
    {
        return keyPair;
    }

    public byte[] getEncodedPublicKey()
    {
        return publicKeyEncoder.getEncoded(keyPair.getPublic());
    }
}