package gnu.crypto.mac;
// ----------------------------------------------------------------------------
// $Id: IMac.java,v 1.4 2005/10/06 04:24:16 rsdio Exp $
//
// Copyright (C) 2001, 2002, 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.
//
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// 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
//
// Free Software Foundation Inc.,
// 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
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// you permission to link this library with independent modules to
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// do so, delete this exception statement from your version.
// ----------------------------------------------------------------------------
import java.util.Map;
import java.security.InvalidKeyException;
/**
* <p>The basic visible methods of any MAC (Message Authentication Code)
* algorithm.</p>
*
* <p>A <i>MAC</i> provides a way to check the integrity of information
* transmitted over, or stored in, an unreliable medium, based on a secret key.
* Typically, <i>MAC</i>s are used between two parties, that share a common
* secret key, in order to validate information transmitted between them.</p>
*
* <p>When a <i>MAC</i> algorithm is based on a cryptographic hash function, it
* is then called to a <i>HMAC</i> (Hashed Message Authentication Code) --see
* <a href="http://www.ietf.org/rfc/rfc-2104.txt">RFC-2104</a>.</p>
*
* Another type of <i>MAC</i> algorithms exist: UMAC or <i>Universal Message
* Authentication Code</i>, described in
* <a href="http://www.ietf.org/internet-drafts/draft-krovetz-umac-01.txt">
* draft-krovetz-umac-01.txt</a>.</p>
*
* <p>With <i>UMAC</i>s, the sender and receiver share a common secret key (the
* <i>MAC</i> key) which determines:</p>
*
* <ul>
* <li>The key for a <i>universal hash function</i>. This hash function is
* <i>non-cryptographic</i>, in the sense that it does not need to have any
* cryptographic <i>hardness</i> property. Rather, it needs to satisfy some
* combinatorial property, which can be proven to hold without relying on
* unproven hardness assumptions.</li>
*
* <li>The key for a <i>pseudorandom function</i>. This is where one needs a
* cryptographic hardness assumption. The pseudorandom function may be
* obtained from a <i>block cipher</i> or a <i>cryptographic hash function</i>.
* </li>
* </ul>
*
* <p>References:</p>
*
* <ol>
* <li><a href="http://www.ietf.org/rfc/rfc-2104.txt">RFC 2104</a>HMAC:
* Keyed-Hashing for Message Authentication.<br>
* H. Krawczyk, M. Bellare, and R. Canetti.</li>
*
* <li><a href="http://www.ietf.org/internet-drafts/draft-krovetz-umac-01.txt">
* UMAC</a>: Message Authentication Code using Universal Hashing.<br>
* T. Krovetz, J. Black, S. Halevi, A. Hevia, H. Krawczyk, and P. Rogaway.</li>
* </ol>
*
* @version $Revision: 1.4 $
*/
public interface IMac {
// Constants
// -------------------------------------------------------------------------
/**
* Property name of the user-supplied key material. The value associated to
* this property name is taken to be a byte array.
*/
String MAC_KEY_MATERIAL = "gnu.crypto.mac.key.material";
/**
* <p>Property name of the desired truncated output size in bytes. The value
* associated to this property name is taken to be an integer. If no value
* is specified in the attributes map at initialisation time, then all bytes
* of the underlying hash algorithm's output are emitted.</p>
*
* <p>This implementation, follows the recommendation of the <i>RFC 2104</i>
* authors; specifically:</p>
*
* <pre>
* We recommend that the output length t be not less than half the
* length of the hash output (to match the birthday attack bound)
* and not less than 80 bits (a suitable lower bound on the number
* of bits that need to be predicted by an attacker).
* </pre>
*/
String TRUNCATED_SIZE = "gnu.crypto.mac.truncated.size";
// Methods
// -------------------------------------------------------------------------
/**
* <p>Returns the canonical name of this algorithm.</p>
*
* @return the canonical name of this algorithm.
*/
String name();
/**
* <p>Returns the output length in bytes of this <i>MAC</i> algorithm.</p>
*
* @return the output length in bytes of this <i>MAC</i> algorithm.
*/
int macSize();
/**
* <p>Initialises the algorithm with designated attributes. Permissible names
* and values are described in the class documentation above.</p>
*
* @param attributes a set of name-value pairs that describe the desired
* future instance behaviour.
* @exception InvalidKeyException if the key data is invalid.
* @exception IllegalStateException if the instance is already initialised.
* @see #MAC_KEY_MATERIAL
*/
void init(Map attributes)
throws InvalidKeyException, IllegalStateException;
/**
* <p>Continues a <i>MAC</i> operation using the input byte.</p>
*
* @param b the input byte to digest.
*/
void update(byte b);
/**
* <p>Continues a <i>MAC</i> operation, by filling the buffer, processing
* data in the algorithm's MAC_SIZE-bit block(s), updating the context and
* count, and buffering the remaining bytes in buffer for the next
* operation.</p>
*
* @param in the input block.
* @param offset start of meaningful bytes in input block.
* @param length number of bytes, in input block, to consider.
*/
void update(byte[] in, int offset, int length);
/**
* <p>Completes the <i>MAC</i> by performing final operations such as
* padding and resetting the instance.</p>
*
* @return the array of bytes representing the <i>MAC</i> value.
*/
byte[] digest();
/**
* <p>Resets the algorithm instance for re-initialisation and use with other
* characteristics. This method always succeeds.</p>
*/
void reset();
/**
* <p>A basic test. Ensures that the MAC of a pre-determined message is equal
* to a known pre-computed value.</p>
*
* @return <code>true</code> if the implementation passes a basic self-test.
* Returns <code>false</code> otherwise.
*/
boolean selfTest();
/**
* <p>Returns a clone copy of this instance.</p>
*
* @return a clone copy of this instance.
*/
Object clone() throws CloneNotSupportedException;
}