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.asn1;

import java.io.IOException;
import java.io.OutputStream;


Stream that outputs encoding based on distinguished encoding rules.

/**
 * Stream that outputs encoding based on distinguished encoding rules.
 */
public class DEROutputStream
    extends ASN1OutputStream
{
    public DEROutputStream(
        OutputStream    os)
    {
        super(os);
    }

    public void writeObject(
        ASN1Encodable obj)
        throws IOException
    {
        if (obj != null)
        {
            obj.toASN1Primitive().toDERObject().encode(this);
        }
        else
        {
            throw new IOException("null object detected");
        }
    }

    ASN1OutputStream getDERSubStream()
    {
        return this;
    }

    ASN1OutputStream getDLSubStream()
    {
        return this;
    }
}