mirror of git://gcc.gnu.org/git/gcc.git
221 lines
7.0 KiB
Java
221 lines
7.0 KiB
Java
/* DESKeySpec -- Keys for DES.
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Copyright (C) 2004 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package javax.crypto.spec;
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import java.security.InvalidKeyException;
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import java.security.spec.KeySpec;
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/**
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* This class is a transparent wrapper for DES keys, which are arrays
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* of 8 bytes.
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*
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* @author Casey Marshall (csm@gnu.org)
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* @since 1.4
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*/
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public class DESKeySpec implements KeySpec
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{
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// Constants.
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// ------------------------------------------------------------------------
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/**
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* The length of a DES key, in bytes.
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*/
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public static final int DES_KEY_LEN = 8;
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/**
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* The key bytes.
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*/
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private byte[] key;
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// Constructors.
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// ------------------------------------------------------------------------
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/**
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* Create a new DES key spec, copying the first 8 bytes from the
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* byte array.
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*
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* @param key The key bytes.
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* @throws java.security.InvalidKeyException If there are less than 8
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* bytes in the array.
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*/
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public DESKeySpec(byte[] key) throws InvalidKeyException
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{
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this(key, 0);
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}
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/**
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* Create a new DES key spec, starting at <code>offset</code> in
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* the byte array. The first 8 bytes starting at <code>offset</code>
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* are copied.
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*
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* @param key The key bytes.
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* @param offset The offset into the byte array at which to begin.
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* @throws java.security.InvalidKeyException If there are less than 8
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* bytes starting at <code>offset</code>.
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*/
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public DESKeySpec(byte[] key, int offset) throws InvalidKeyException
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{
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if (key.length - offset < DES_KEY_LEN)
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{
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throw new InvalidKeyException("DES keys must be 8 bytes long");
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}
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this.key = new byte[DES_KEY_LEN];
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System.arraycopy(key, offset, this.key, 0, DES_KEY_LEN);
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}
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// Class methods.
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// ------------------------------------------------------------------------
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/**
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* Returns whether or not the given key is <i>parity adjusted</i>;
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* i.e. every byte in the key has an odd number of "1" bits.
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*
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* @param key The key bytes, considered between <code>[offset,
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* offset+7]</code>
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* @param offset The offset into the byte array at which to begin.
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* @return True if all bytes have an odd number of "1" bits.
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* @throws java.security.InvalidKeyException If there are not enough
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* bytes in the array.
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*/
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public static boolean isParityAdjusted(byte[] key, int offset)
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throws InvalidKeyException
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{
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if (key.length - offset < DES_KEY_LEN)
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{
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throw new InvalidKeyException("DES keys must be 8 bytes long");
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}
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boolean parity = false;
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boolean oddbits = false;
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for (int i = 0; i < DES_KEY_LEN; i++)
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{
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oddbits = false;
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for (int j = 0; j < 8; j++)
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{
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oddbits ^= (key[i+offset] & 1 << j) != 0;
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}
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parity &= oddbits;
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}
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return parity;
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}
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/**
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* One-half of the weak and semiweak DES keys (the other half are the
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* complements of these).
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*/
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private static final byte[][] WEAK_KEYS = new byte[][] {
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{ 0, 0, 0, 0, 0, 0, 0, 0 }, // 0000 0000 0000 0000
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{ -1, -1, -1, -1, 0, 0, 0, 0 }, // ffff ffff 0000 0000
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{ 1, 1, 1, 1, 1, 1, 1, 1 }, // 0101 0101 0101 0101
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{ 31, 31, 31, 31, 14, 14, 14, 14 }, // 1f1f 1f1f 0e0e 0e0e
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{ 1, -2, 1, -2, 1, -2, 1, -2 }, // 01fe 01fe 01fe 01fe
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{ 31, -32, 31, -32, -32, 31, -32, 31 }, // 1fe0 1fe0 0e1f 0e1f
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{ 1, -32, 1, -32, 1, -15, 1, -15 }, // 01e0 01e0 01f1 01f1
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{ 31, -2, 31, -2, 14, -2, 14, -2 }, // 1ffe 1ffe 0efe 0efe
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{ 1, 31, 1, 31, 1, 14, 1, 14 }, // 011f 011f 010e 010e
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{ -32, -2, -32, -2, -15, -2, -15, -2 }, // e0fe e0fe f1fe f1fe
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};
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/**
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* Tests if the bytes between <code>[offset, offset+7]</code>
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* constitute a weak or semi-weak DES key.
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*
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* @param key The key bytes to check.
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* @param offset The offset in the byte array to start.
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* @return true If the key bytes are a weak key.
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*/
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public static boolean isWeak(byte[] key, int offset)
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throws InvalidKeyException
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{
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if (key.length - offset < DES_KEY_LEN)
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{
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throw new InvalidKeyException("DES keys must be 8 bytes long");
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}
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for (int i = 0; i < WEAK_KEYS.length; i++)
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{
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if (equalsOrComplementEquals(key, offset, WEAK_KEYS[i]))
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{
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return true;
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}
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}
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return false;
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}
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/**
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* This method returns true if the first 8 bytes starting at
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* <code>off</code> in <code>a</code> equal the first 8 bytes in
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* <code>b</code>, or equal the <i>complement</i> of the first 8 bytes
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* in <code>b</code>.
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*
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* @param a The first byte array.
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* @param off The index into the first byte array.
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* @param b The second byte array.
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* @return <code>a == b || a == ~b</code>
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*/
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private static boolean equalsOrComplementEquals(byte[] a, int off, byte[] b)
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{
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boolean result = true;
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for (int i = 0; i < DES_KEY_LEN; i++)
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{
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result &= a[off+i] == b[i];
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}
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if (result) return true;
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result = true;
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for (int i = 0; i < DES_KEY_LEN; i++)
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{
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result &= a[off+i] == (~b[i]);
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}
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return result;
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}
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// Instance methods.
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// ------------------------------------------------------------------------
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/**
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* Return the key as a byte array. This method does not copy the byte
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* array.
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*
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* @return The key bytes.
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*/
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public byte[] getKey()
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{
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return key;
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}
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}
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