| /* SHA1PRNG.java --- Secure Random SPI SHA1PRNG |
| Copyright (C) 1999, 2001, 2003 Free Software Foundation, Inc. |
| |
| This file is 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, 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; see the file COPYING. If not, write to the |
| Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
| 02111-1307 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.provider; |
| |
| import java.util.Random; |
| import java.security.SecureRandomSpi; |
| import java.security.MessageDigest; |
| import java.security.NoSuchAlgorithmException; |
| import java.io.Serializable; |
| |
| public class SHA1PRNG extends SecureRandomSpi implements Serializable |
| { |
| MessageDigest digest; |
| byte seed[]; |
| byte data[]; |
| int seedpos; |
| int datapos; |
| private boolean seeded = false; // set to true when we seed this |
| |
| public SHA1PRNG() |
| { |
| try { |
| digest = MessageDigest.getInstance("SHA"); |
| } catch ( NoSuchAlgorithmException nsae) { |
| // System.out.println("Failed to find SHA Message Digest: " + nsae); |
| // nsae.printStackTrace(); |
| throw new InternalError ("no SHA implementation found"); |
| } |
| |
| seed = new byte[20]; |
| seedpos = 0; |
| data = new byte[40]; |
| datapos = 20; // try to force hashing a first block |
| } |
| |
| public void engineSetSeed(byte[] seed) |
| { |
| for(int i = 0; i < seed.length; i++) |
| this.seed[seedpos++ % 20] ^= seed[i]; |
| seedpos %= 20; |
| |
| } |
| |
| public void engineNextBytes(byte[] bytes) |
| { |
| ensureIsSeeded (); |
| int loc = 0; |
| while (loc < bytes.length) |
| { |
| int copy = Math.min (bytes.length - loc, 20 - datapos); |
| |
| if (copy > 0) |
| { |
| System.arraycopy (data, datapos, bytes, loc, copy); |
| datapos += copy; |
| loc += copy; |
| } |
| else |
| { |
| // No data ready for copying, so refill our buffer. |
| System.arraycopy( seed, 0, data, 20, 20); |
| byte[] digestdata = digest.digest( data ); |
| System.arraycopy( digestdata, 0, data, 0, 20); |
| datapos = 0; |
| } |
| } |
| } |
| |
| public byte[] engineGenerateSeed(int numBytes) |
| { |
| byte tmp[] = new byte[numBytes]; |
| |
| engineNextBytes( tmp ); |
| return tmp; |
| } |
| |
| private void ensureIsSeeded() |
| { |
| if (!seeded) |
| { |
| new Random(0L).nextBytes(seed); |
| |
| byte[] digestdata = digest.digest(data); |
| System.arraycopy(digestdata, 0, data, 0, 20); |
| |
| seeded = true; |
| } |
| } |
| |
| } |