| /* MDGenerator.java -- |
| Copyright (C) 2001, 2002, 2006 Free Software Foundation, Inc. |
| |
| This file is a part of GNU Classpath. |
| |
| GNU Classpath 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 of the License, or (at |
| your option) any later version. |
| |
| GNU Classpath 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 GNU Classpath; if not, write to the Free Software |
| Foundation, Inc., 51 Franklin St, 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 |
| combination. |
| |
| As a special exception, the copyright holders of this library give you |
| permission to link this library with independent modules to produce an |
| executable, regardless of the license terms of these independent |
| modules, and to copy and distribute the resulting executable under |
| terms of your choice, provided that you also meet, for each linked |
| independent module, the terms and conditions of the license of that |
| module. An independent module is a module which is not derived from |
| or based on this library. If you modify this library, you may extend |
| this exception to your version of the library, but you are not |
| obligated to do so. If you do not wish to do so, delete this |
| exception statement from your version. */ |
| |
| |
| package gnu.java.security.prng; |
| |
| import gnu.java.security.Registry; |
| import gnu.java.security.hash.HashFactory; |
| import gnu.java.security.hash.IMessageDigest; |
| |
| import java.util.Map; |
| |
| /** |
| * A simple pseudo-random number generator that relies on a hash algorithm, that |
| * (a) starts its operation by hashing a <code>seed</code>, and then (b) |
| * continuously re-hashing its output. If no hash algorithm name is specified in |
| * the {@link Map} of attributes used to initialise the instance then the |
| * SHA-160 algorithm is used as the underlying hash function. Also, if no |
| * <code>seed</code> is given, an empty octet sequence is used. |
| */ |
| public class MDGenerator |
| extends BasePRNG |
| implements Cloneable |
| { |
| /** Property name of underlying hash algorithm for this generator. */ |
| public static final String MD_NAME = "gnu.crypto.prng.md.hash.name"; |
| |
| /** Property name of seed material. */ |
| public static final String SEEED = "gnu.crypto.prng.md.seed"; |
| |
| /** The underlying hash instance. */ |
| private IMessageDigest md; |
| |
| /** Trivial 0-arguments constructor. */ |
| public MDGenerator() |
| { |
| super(Registry.MD_PRNG); |
| } |
| |
| public void setup(Map attributes) |
| { |
| // find out which hash to use |
| String underlyingMD = (String) attributes.get(MD_NAME); |
| if (underlyingMD == null) |
| { |
| if (md == null) |
| { // happy birthday |
| // ensure we have a reliable implementation of this hash |
| md = HashFactory.getInstance(Registry.SHA160_HASH); |
| } |
| else // a clone. reset it for reuse |
| md.reset(); |
| } |
| else // ensure we have a reliable implementation of this hash |
| md = HashFactory.getInstance(underlyingMD); |
| // get the seeed |
| byte[] seed = (byte[]) attributes.get(SEEED); |
| if (seed == null) |
| seed = new byte[0]; |
| |
| md.update(seed, 0, seed.length); |
| } |
| |
| public void fillBlock() throws LimitReachedException |
| { |
| IMessageDigest mdc = (IMessageDigest) md.clone(); |
| buffer = mdc.digest(); |
| md.update(buffer, 0, buffer.length); |
| } |
| |
| public void addRandomByte(final byte b) |
| { |
| if (md == null) |
| throw new IllegalStateException("not initialized"); |
| md.update(b); |
| } |
| |
| public void addRandomBytes(final byte[] buf, final int off, final int len) |
| { |
| if (md == null) |
| throw new IllegalStateException("not initialized"); |
| md.update(buf, off, len); |
| } |
| |
| public Object clone() throws CloneNotSupportedException |
| { |
| MDGenerator result = (MDGenerator) super.clone(); |
| if (this.md != null) |
| result.md = (IMessageDigest) this.md.clone(); |
| |
| return result; |
| } |
| } |