bouncycastle 是一个JAVA安全提供者

				package org.bouncycastle.asn1;								import java.io.IOException;								/**				 * A NULL object.				 */				public class DERNull				    extends ASN1Null				{				    byte[]  zeroBytes = new byte[0];								    public DERNull()				    {				    }								    void encode(				        DEROutputStream  out)				        throws IOException				    {				        out.writeEncoded(NULL, zeroBytes);				    }				    				    public boolean equals(				        Object o)				    {				        if ((o == null) || !(o instanceof DERNull))				        {				            return false;				        }				        				        return true;				    }				    				    public int hashCode()				    {				        return 0;				    }				}