package gnu.crypto.sig;

// ----------------------------------------------------------------------------
// $Id: ISignature.java,v 1.8 2005/10/06 04:24:18 rsdio Exp $
//
// Copyright (C) 2001, 2002, 2003 Free Software Foundation, Inc.
//
// This file is part of GNU Crypto.
//
// GNU Crypto is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// GNU Crypto 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 for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program; see the file COPYING.  If not, write to the
//
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//    51 Franklin Street, Fifth Floor,
//    Boston, MA 02110-1301
//    USA
//
// Linking this library statically or dynamically with other modules is
// making a combined work based on this library.  Thus, the terms and
// conditions of the GNU General Public License cover the whole
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// you permission to link this library with independent modules to
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// ----------------------------------------------------------------------------

import java.util.Map;

/**
 * <p>The visible methods of every signature-with-appendix scheme.</p>
 *
 * <p>The Handbook of Applied Cryptography (HAC), by A. Menezes & al. states:
 * "Digital signature schemes which require the message as input to the
 * verification algorithm are called <i>digital signature schemes with
 * appendix</i>. ... They rely on cryptographic hash functions rather than
 * customised redundancy functions, and are less prone to existential forgery
 * attacks."</p>
 *
 * <p>References:</p>
 * <ol>
 *    <li><a href="http://www.cacr.math.uwaterloo.ca/hac/">Handbook of Applied
 *    Cryptography</a>, Alfred J. Menezes, Paul C. van Oorschot and Scott A.
 *    Vanstone. Section 11.2.2 Digital signature schemes with appendix.</li>
 * </ol>
 *
 * @version $Revision: 1.8 $
 */
public interface ISignature extends Cloneable {

   // Constants
   // -------------------------------------------------------------------------

   /** Property name of the verifier's public key. */
   public static final String VERIFIER_KEY = "gnu.crypto.sig.public.key";

   /** Property name of the signer's private key. */
   public static final String SIGNER_KEY = "gnu.crypto.sig.private.key";

   /**
    * Property name of an optional {@link java.security.SecureRandom},
    * {@link java.util.Random}, or {@link gnu.crypto.prng.IRandom} instance to
    * use. The default is to use a classloader singleton from
    * {@link gnu.crypto.util.PRNG}.
    */
   public static final String SOURCE_OF_RANDOMNESS = "gnu.crypto.sig.prng";

   // Methods
   // -------------------------------------------------------------------------

   /**
    * <p>Returns the canonical name of this signature scheme.</p>
    *
    * @return the canonical name of this instance.
    */
   String name();

   /**
    * <p>Initialises this instance for signature verification.</p>
    *
    * @param attributes the attributes to use for setting up this instance.
    * @throws IllegalArgumentException if the designated public key is not
    * appropriate for this signature scheme.
    * @see #SOURCE_OF_RANDOMNESS
    * @see #VERIFIER_KEY
    */
   void setupVerify(Map attributes) throws IllegalArgumentException;

   /**
    * <p>Initialises this instance for signature generation.</p>
    *
    * @param attributes the attributes to use for setting up this instance.
    * @throws IllegalArgumentException if the designated private key is not
    * appropriate for this signature scheme.
    * @see #SOURCE_OF_RANDOMNESS
    * @see #SIGNER_KEY
    */
   void setupSign(Map attributes) throws IllegalArgumentException;

   /**
    * <p>Digests one byte of a message for signing or verification purposes.</p>
    *
    * @param b the message byte to digest.
    * @throws IllegalStateException if this instance was not setup for
    * signature generation/verification.
    */
   void update(byte b) throws IllegalStateException;

   /**
    * <p>Digests a sequence of bytes from a message for signing or verification
    * purposes.</p>
    *
    * @param buffer the byte sequence to consider.
    * @param offset the byte poisition in <code>buffer</code> of the first byte
    * to consider.
    * @param length the number of bytes in <code>buffer</code> starting from the
    * byte at index <code>offset</code> to digest.
    * @throws IllegalStateException if this instance was not setup for
    * signature generation/verification.
    */
   void update(byte[] buffer, int offset, int length)
   throws IllegalStateException;

   /**
    * <p>Terminates a signature generation phase by digesting and processing the
    * context of the underlying message digest algorithm instance.</p>
    *
    * @return a {@link Object} representing the native output of the signature
    * scheme implementation.
    * @throws IllegalStateException if this instance was not setup for
    * signature generation.
    */
   Object sign() throws IllegalStateException;

   /**
    * <p>Terminates a signature verification phase by digesting and processing
    * the context of the underlying message digest algorithm instance.</p>
    *
    * @param signature a native signature object previously generated by an
    * invocation of the <code>sign()</code> method.
    * @return <code>true</code> iff the outpout of the verification phase
    * confirms that the designated signature object has been generated using the
    * corresponding public key of the recepient.
    * @throws IllegalStateException if this instance was not setup for
    * signature verification.
    */
   boolean verify(Object signature) throws IllegalStateException;

   /**
    * <p>Returns a clone copy of this instance.</p>
    *
    * @return a clone copy of this instance.
    */
   Object clone();
}
