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.spec;

import java.math.BigInteger;


Elliptic Curve private key specification.

/**
 * Elliptic Curve private key specification.
 */
public class ECPrivateKeySpec
    extends ECKeySpec
{
    private BigInteger    d;

    
base constructor

Params:
  • d – the private number for the key.
  • spec – the domain parameters for the curve being used.
/**
     * base constructor
     *
     * @param d the private number for the key.
     * @param spec the domain parameters for the curve being used.
     */
    public ECPrivateKeySpec(
        BigInteger      d,
        ECParameterSpec spec)
    {
        super(spec);

        this.d = d;
    }

    
return the private number D

/**
     * return the private number D
     */
    public BigInteger getD()
    {
        return d;
    }
}