/*
 *   
 *
 * Copyright  1990-2006 Sun Microsystems, Inc. All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
 * 
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 only, as published by the Free Software Foundation. 
 * 
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License version 2 for more details (a copy is
 * included at /legal/license.txt). 
 * 
 * You should have received a copy of the GNU General Public License
 * version 2 along with this work; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA 
 * 
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
 * Clara, CA 95054 or visit www.sun.com if you need additional
 * information or have any questions. 
 */

package java.security;

/**
 * The Key interface is the top-level interface for all keys. It
 * defines the functionality shared by all key objects. All keys
 * have three characteristics:
 *
 * <UL>
 *
 * <LI>An Algorithm
 *
 * <P>This is the key algorithm for that key. The key algorithm is usually
 * an encryption or asymmetric operation algorithm (such as DSA or
 * RSA), which will work with those algorithms and with related
 * algorithms (such as MD5 with RSA, SHA-1 with RSA, Raw DSA, etc.)
 *
 * <LI>An Encoded Form
 *
 * <P>This is an external encoded form for the key used when a standard
 * representation of the key is needed outside the Java Virtual Machine,
 * as when transmitting the key to some other party. The key
 * is encoded according to a standard format (such as 
 * X.509 <code>SubjectPublicKeyInfo</code>).
 * Note: The syntax of the ASN.1 type <code>SubjectPublicKeyInfo</code> 
 * is defined as follows:
 *
 * <pre>
 * SubjectPublicKeyInfo ::= SEQUENCE {
 *   algorithm AlgorithmIdentifier,
 *   subjectPublicKey BIT STRING }
 *
 * AlgorithmIdentifier ::= SEQUENCE {
 *   algorithm OBJECT IDENTIFIER,
 *   parameters ANY DEFINED BY algorithm OPTIONAL }
 * </pre>
 * 
 * For more information, see 
 * <a href="http://www.ietf.org/rfc/rfc2459.txt">RFC 2459: 
 * Internet X.509 Public Key Infrastructure Certificate and CRL Profile</a>.
 * <P>
 *
 * <LI>A Format
 *
 * <P>This is the name of the format of the encoded key. 
 *
 * </UL>
 *
 * Keys are generally obtained through key generators and certificates.
 * Keys may also be obtained from key specifications (transparent
 * representations of the underlying key material) through the use of a key
 * factory.
 *
 */

public interface Key  {

    /**
     * Returns the standard algorithm name for this key. 
     * For example, "DSA" would indicate that this key is a DSA key. 
     * See Appendix A in the Java Cryptography Architecture API 
     * Specification & Reference for information about standard algorithm names
     *
     * @return the name of the algorithm associated with this key.
     */
    public String getAlgorithm();
    
    
    /**
     * Returns the name of the primary encoding format of this key, or null 
     * if this key does not support encoding. The primary encoding format is 
     * named in terms of the appropriate ASN.1 data format, if an ASN.1 
     * specification for this key exists. For example, the name of the ASN.1 
     * data format for public keys is <I>SubjectPublicKeyInfo</I>, as defined by
     * the X.509 standard; in this case, the returned format is
     * <code>"X.509"</code>.
     * Similarly, the name of the ASN.1 data format for private keys is 
     * <I>PrivateKeyInfo</I>, as defined by the PKCS #8 standard; in this case, 
     * the returned format is <code>"PKCS#8"</code>. 
     *
     * @return the primary encoding format of the key.
     */
    public String getFormat();
    
    /**
     * Returns the key in its primary encoding format, or null 
     * if this key does not support encoding. 
     *
     * @return the encoded key, or null if the key does not support encoding.
     */
    public byte[] getEncoded();
  
}
