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.params;

import java.math.BigInteger;

public class GOST3410PrivateKeyParameters
        extends GOST3410KeyParameters
{
    private BigInteger      x;

    public GOST3410PrivateKeyParameters(
        BigInteger      x,
        GOST3410Parameters   params)
    {
        super(true, params);

        this.x = x;
    }

    public BigInteger getX()
    {
        return x;
    }
}