/*
 * @(#)Key.java	1.57 06/04/21
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

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.)
 * The name of the algorithm of a key is obtained using the
 * {@link #getAlgorithm() getAlgorithm} method.<P>
 *
 * <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> or PKCS#8), and
 * is returned using the {@link #getEncoded() getEncoded} method.
 * 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. It is returned
 * by the {@link #getFormat() getFormat} method.<P>
 *
 * </UL>
 *
 * Keys are generally obtained through key generators, certificates,
 * or various Identity classes used to manage keys.
 * Keys may also be obtained from key specifications (transparent
 * representations of the underlying key material) through the use of a key
 * factory (see {@link KeyFactory}).
 *
 * <p> A Key should use KeyRep as its serialized representation.
 * Note that a serialized Key may contain sensitive information
 * which should not be exposed in untrusted environments.  See the
 * <a href="../../../platform/serialization/spec/security.html">
 * Security Appendix</a>
 * of the Serialization Specification for more information.
 *
 * @see PublicKey
 * @see PrivateKey
 * @see KeyPair
 * @see KeyPairGenerator
 * @see KeyFactory
 * @see KeyRep
 * @see java.security.spec.KeySpec
 * @see Identity
 * @see Signer
 *
 * @version 1.57 06/04/21
 * @author Benjamin Renaud
 */

public interface Key extends java.io.Serializable {

    // Declare serialVersionUID to be compatible with JDK1.1

   /**
    * The class fingerprint that is set to indicate 
    * serialization compatibility with a previous 
    * version of the class.
    */
    static final long serialVersionUID = 6603384152749567654L;

    /**
     * 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 <a href=
     * "../../../technotes/guides/security/crypto/CryptoSpec.html#AppA">
     * Java Cryptography Architecture API Specification &amp; Reference </a>
     * 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();
}
