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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: */ 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: 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: 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: 116: public byte[] engineGenerateSeed(int numBytes) 117: { 118: byte tmp[] = new byte[numBytes]; 119: 120: engineNextBytes( tmp ); 121: return tmp; 122: } 123: 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: }