1 /* SHA1PRNG.java --- Secure Random SPI SHA1PRNG 2 Copyright (C) 1999, 2001, 2003, 2005 Free Software Foundation, Inc. 3 4 This file is part of GNU Classpath. 5 6 GNU Classpath is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 2, or (at your option) 9 any later version. 10 11 GNU Classpath is distributed in the hope that it will be useful, but 12 WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14 General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with GNU Classpath; see the file COPYING. If not, write to the 18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19 02110-1301 USA. 20 21 Linking this library statically or dynamically with other modules is 22 making a combined work based on this library. Thus, the terms and 23 conditions of the GNU General Public License cover the whole 24 combination. 25 26 As a special exception, the copyright holders of this library give you 27 permission to link this library with independent modules to produce an 28 executable, regardless of the license terms of these independent 29 modules, and to copy and distribute the resulting executable under 30 terms of your choice, provided that you also meet, for each linked 31 independent module, the terms and conditions of the license of that 32 module. An independent module is a module which is not derived from 33 or based on this library. If you modify this library, you may extend 34 this exception to your version of the library, but you are not 35 obligated to do so. If you do not wish to do so, delete this 36 exception statement from your version. */ 37 38 39 package gnu.java.security.provider; 40 41 import java.io.Serializable; 42 import java.security.MessageDigest; 43 import java.security.NoSuchAlgorithmException; 44 import java.security.SecureRandomSpi; 45 import java.util.Random; 46 47 public class SHA1PRNG extends SecureRandomSpi implements Serializable 48 { 49 MessageDigest digest; 50 byte seed[]; 51 byte data[]; 52 int seedpos; 53 int datapos; 54 private boolean seeded = false; // set to true when we seed this 55 /** 56 * The size of seed. 57 */ 58 private static final int SEED_SIZE = 20; 59 /** 60 * The size of data. 61 */ 62 private static final int DATA_SIZE = 40; 63 64 /** 65 * Create a new SHA-1 pseudo-random number generator. 66 */ SHA1PRNG()67 public SHA1PRNG() 68 { 69 try { 70 digest = MessageDigest.getInstance("SHA"); 71 } catch ( NoSuchAlgorithmException nsae) { 72 // System.out.println("Failed to find SHA Message Digest: " + nsae); 73 // nsae.printStackTrace(); 74 throw new InternalError ("no SHA implementation found"); 75 } 76 77 seed = new byte[SEED_SIZE]; 78 seedpos = 0; 79 data = new byte[DATA_SIZE]; 80 datapos = SEED_SIZE; // try to force hashing a first block 81 } 82 engineSetSeed(byte[] seed)83 public void engineSetSeed(byte[] seed) 84 { 85 for(int i = 0; i < seed.length; i++) 86 this.seed[seedpos++ % SEED_SIZE] ^= seed[i]; 87 seedpos %= SEED_SIZE; 88 89 } 90 engineNextBytes(byte[] bytes)91 public void engineNextBytes(byte[] bytes) 92 { 93 ensureIsSeeded (); 94 int loc = 0; 95 while (loc < bytes.length) 96 { 97 int copy = Math.min (bytes.length - loc, SEED_SIZE - datapos); 98 99 if (copy > 0) 100 { 101 System.arraycopy (data, datapos, bytes, loc, copy); 102 datapos += copy; 103 loc += copy; 104 } 105 else 106 { 107 // No data ready for copying, so refill our buffer. 108 System.arraycopy( seed, 0, data, SEED_SIZE, SEED_SIZE); 109 byte[] digestdata = digest.digest( data ); 110 System.arraycopy( digestdata, 0, data, 0, SEED_SIZE); 111 datapos = 0; 112 } 113 } 114 } 115 engineGenerateSeed(int numBytes)116 public byte[] engineGenerateSeed(int numBytes) 117 { 118 byte tmp[] = new byte[numBytes]; 119 120 engineNextBytes( tmp ); 121 return tmp; 122 } 123 ensureIsSeeded()124 private void ensureIsSeeded() 125 { 126 if (!seeded) 127 { 128 new Random(0L).nextBytes(seed); 129 130 byte[] digestdata = digest.digest(data); 131 System.arraycopy(digestdata, 0, data, 0, SEED_SIZE); 132 133 seeded = true; 134 } 135 } 136 137 } 138