http://www.bouncycastle.org/java.html: The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 to JDK 1.8. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.cms;

import org.bouncycastle.util.Selector;

public abstract class RecipientId
    implements Selector
{
    public static final int keyTrans = 0;
    public static final int kek = 1;
    public static final int keyAgree = 2;
    public static final int password = 3;

    private final int type;

    protected RecipientId(int type)
    {
        this.type = type;
    }

    
Return the type code for this recipient ID.

Returns:one of keyTrans, kek, keyAgree, password
/**
     * Return the type code for this recipient ID.
     *
     * @return one of keyTrans, kek, keyAgree, password
     */
    public int getType()
    {
        return type;
    }

    public abstract Object clone();
}