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.pqc.crypto.newhope;

import org.bouncycastle.crypto.engines.ChaChaEngine;
import org.bouncycastle.crypto.params.KeyParameter;
import org.bouncycastle.crypto.params.ParametersWithIV;

class ChaCha20
{
    static void process(byte[] key, byte[] nonce, byte[] buf, int off, int len)
    {
        ChaChaEngine e = new ChaChaEngine(20);
        e.init(true, new ParametersWithIV(new KeyParameter(key), nonce));
        e.processBytes(buf, off, len, buf, off);
    }
}