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Diffstat (limited to 'libjava/classpath/gnu/javax/crypto/prng/ARCFour.java')
| -rw-r--r-- | libjava/classpath/gnu/javax/crypto/prng/ARCFour.java | 161 |
1 files changed, 161 insertions, 0 deletions
diff --git a/libjava/classpath/gnu/javax/crypto/prng/ARCFour.java b/libjava/classpath/gnu/javax/crypto/prng/ARCFour.java new file mode 100644 index 00000000000..22316ec8b9b --- /dev/null +++ b/libjava/classpath/gnu/javax/crypto/prng/ARCFour.java @@ -0,0 +1,161 @@ +/* ARCFour.java -- + Copyright (C) 2002, 2003, 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.javax.crypto.prng; + +import gnu.java.security.Registry; +import gnu.java.security.prng.BasePRNG; +import gnu.java.security.prng.LimitReachedException; + +import java.util.Map; + +/** + * RC4 is a stream cipher developed by Ron Rivest. Until 1994 RC4 was a + * trade secret of RSA Data Security, Inc., when it was released + * anonymously to a mailing list. This version is a descendent of that + * code, and since there is no proof that the leaked version was in fact + * RC4 and because "RC4" is a trademark, it is called "ARCFOUR", short for + * "Allegedly RC4". + * + * <p>This class only implements the <i>keystream</i> of ARCFOUR. To use + * this as a stream cipher, one would say:</p> + * + * <pre> out = in ^ arcfour.nextByte();</pre> + * + * <p>This operation works for encryption and decryption.</p> + * + * <p>References:</p> + * + * <ol> + * <li>Schneier, Bruce: <i>Applied Cryptography: Protocols, Algorithms, + * and Source Code in C, Second Edition.</i> (1996 John Wiley and Sons), + * pp. 397--398. ISBN 0-471-11709-9</li> + * <li>K. Kaukonen and R. Thayer, "A Stream Cipher Encryption Algorithm + * 'Arcfour'", Internet Draft (expired), <a + * href="http://www.mozilla.org/projects/security/pki/nss/draft-kaukonen-cipher-arcfour-03.txt">draft-kaukonen-cipher-arcfour-03.txt</a></li> + * </ol> + */ +public class ARCFour extends BasePRNG implements Cloneable +{ + + // Constants and variables. + // ----------------------------------------------------------------------- + + /** The attributes property name for the key bytes. */ + public static final String ARCFOUR_KEY_MATERIAL = "gnu.crypto.prng.arcfour.key-material"; + + /** The size of the internal S-box. */ + public static final int ARCFOUR_SBOX_SIZE = 256; + + /** The S-box. */ + private byte[] s; + + private byte m, n; + + // Constructors. + // ----------------------------------------------------------------------- + + /** Default 0-arguments constructor. */ + public ARCFour() + { + super(Registry.ARCFOUR_PRNG); + } + + // Methods implementing BasePRNG. + // ----------------------------------------------------------------------- + + public void setup(Map attributes) + { + byte[] kb = (byte[]) attributes.get(ARCFOUR_KEY_MATERIAL); + + if (kb == null) + { + throw new IllegalArgumentException("ARCFOUR needs a key"); + } + + s = new byte[ARCFOUR_SBOX_SIZE]; + m = n = 0; + byte[] k = new byte[ARCFOUR_SBOX_SIZE]; + + for (int i = 0; i < ARCFOUR_SBOX_SIZE; i++) + { + s[i] = (byte) i; + } + + if (kb.length > 0) + { + for (int i = 0, j = 0; i < ARCFOUR_SBOX_SIZE; i++) + { + k[i] = kb[j++]; + if (j >= kb.length) + j = 0; + } + } + + for (int i = 0, j = 0; i < ARCFOUR_SBOX_SIZE; i++) + { + j = j + s[i] + k[i]; + byte temp = s[i]; + s[i] = s[j & 0xff]; + s[j & 0xff] = temp; + } + + buffer = new byte[ARCFOUR_SBOX_SIZE]; + try + { + fillBlock(); + } + catch (LimitReachedException wontHappen) + { + } + } + + public void fillBlock() throws LimitReachedException + { + for (int i = 0; i < buffer.length; i++) + { + m++; + n = (byte) (n + s[m & 0xff]); + byte temp = s[m & 0xff]; + s[m & 0xff] = s[n & 0xff]; + s[n & 0xff] = temp; + temp = (byte) (s[m & 0xff] + s[n & 0xff]); + buffer[i] = s[temp & 0xff]; + } + } +}
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