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.jcajce.provider.symmetric;

import org.bouncycastle.crypto.CipherKeyGenerator;
import org.bouncycastle.crypto.engines.SkipjackEngine;
import org.bouncycastle.crypto.macs.CBCBlockCipherMac;
import org.bouncycastle.crypto.macs.CFBBlockCipherMac;
import org.bouncycastle.jcajce.provider.config.ConfigurableProvider;
import org.bouncycastle.jcajce.provider.symmetric.util.BaseBlockCipher;
import org.bouncycastle.jcajce.provider.symmetric.util.BaseKeyGenerator;
import org.bouncycastle.jcajce.provider.symmetric.util.BaseMac;
import org.bouncycastle.jcajce.provider.symmetric.util.IvAlgorithmParameters;
import org.bouncycastle.jcajce.provider.util.AlgorithmProvider;

public final class Skipjack
{
    private Skipjack()
    {
    }
    
    public static class ECB
        extends BaseBlockCipher
    {
        public ECB()
        {
            super(new SkipjackEngine());
        }
    }

    public static class KeyGen
        extends BaseKeyGenerator
    {
        public KeyGen()
        {
            super("Skipjack", 80, new CipherKeyGenerator());
        }
    }

    public static class AlgParams
        extends IvAlgorithmParameters
    {
        protected String engineToString()
        {
            return "Skipjack IV";
        }
    }

    public static class Mac
        extends BaseMac
    {
        public Mac()
        {
            super(new CBCBlockCipherMac(new SkipjackEngine()));
        }
    }

    public static class MacCFB8
        extends BaseMac
    {
        public MacCFB8()
        {
            super(new CFBBlockCipherMac(new SkipjackEngine()));
        }
    }

    public static class Mappings
        extends AlgorithmProvider
    {
        private static final String PREFIX = Skipjack.class.getName();

        public Mappings()
        {
        }

        public void configure(ConfigurableProvider provider)
        {

            provider.addAlgorithm("Cipher.SKIPJACK", PREFIX + "$ECB");
            provider.addAlgorithm("KeyGenerator.SKIPJACK", PREFIX + "$KeyGen");
            provider.addAlgorithm("AlgorithmParameters.SKIPJACK", PREFIX + "$AlgParams");
            provider.addAlgorithm("Mac.SKIPJACKMAC", PREFIX + "$Mac");
            provider.addAlgorithm("Alg.Alias.Mac.SKIPJACK", "SKIPJACKMAC");
            provider.addAlgorithm("Mac.SKIPJACKMAC/CFB8", PREFIX + "$MacCFB8");
            provider.addAlgorithm("Alg.Alias.Mac.SKIPJACK/CFB8", "SKIPJACKMAC/CFB8");

        }
    }
}