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Diffstat (limited to 'libjava/classpath/gnu/javax/crypto/mode/CTR.java')
| -rw-r--r-- | libjava/classpath/gnu/javax/crypto/mode/CTR.java | 221 |
1 files changed, 221 insertions, 0 deletions
diff --git a/libjava/classpath/gnu/javax/crypto/mode/CTR.java b/libjava/classpath/gnu/javax/crypto/mode/CTR.java new file mode 100644 index 00000000000..49f4b9f3c2a --- /dev/null +++ b/libjava/classpath/gnu/javax/crypto/mode/CTR.java @@ -0,0 +1,221 @@ +/* CTR.java -- + Copyright (C) 2001, 2002, 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.mode; + +import gnu.java.security.Registry; +import gnu.java.security.util.Sequence; + +import gnu.javax.crypto.cipher.IBlockCipher; + +import java.math.BigInteger; +import java.util.Arrays; +import java.util.Iterator; + +/** + * <p>The implementation of the Counter Mode.</p> + * + * <p>The algorithm steps are formally described as follows:</p> + * + * <pre> + * CTR Encryption: O[j] = E(K)(T[j]); for j = 1, 2...n; + * C[j] = P[j] ^ O[j]; for j = 1, 2...n. + * CTR Decryption: O[j] = E(K)(T[j]); for j = 1, 2...n; + * P[j] = C[j] ^ O[j]; for j = 1, 2...n. + * </pre> + * + * <p>where <code>P</code> is the plaintext, <code>C</code> is the ciphertext, + * <code>E(K)</code> is the underlying block cipher encryption function + * parametrised with the session key <code>K</code>, and <code>T</code> is the + * <i>Counter</i>.</p> + * + * <p>This implementation, uses a standard incrementing function with a step of + * 1, and an initial value similar to that described in the NIST document.</p> + * + * <p>References:</p> + * + * <ol> + * <li><a href="http://csrc.nist.gov/encryption/modes/Recommendation/Modes01.pdf"> + * Recommendation for Block Cipher Modes of Operation Methods and Techniques</a>, + * Morris Dworkin.</li> + * </ol> + */ +public class CTR extends BaseMode implements Cloneable +{ + + // Constants and variables + // ------------------------------------------------------------------------- + + /** The current counter. */ + // private BigInteger T; + private int off; + + private byte[] counter, enc; + + // Constructor(s) + // ------------------------------------------------------------------------- + + /** + * <p>Trivial package-private constructor for use by the Factory class.</p> + * + * @param underlyingCipher the underlying cipher implementation. + * @param cipherBlockSize the underlying cipher block size to use. + */ + CTR(IBlockCipher underlyingCipher, int cipherBlockSize) + { + super(Registry.CTR_MODE, underlyingCipher, cipherBlockSize); + } + + /** + * <p>Private constructor for cloning purposes.</p> + * + * @param that the instance to clone. + */ + private CTR(CTR that) + { + this((IBlockCipher) that.cipher.clone(), that.cipherBlockSize); + } + + // Class methods + // ------------------------------------------------------------------------- + + // Cloneable interface implementation + // ------------------------------------------------------------------------- + + public Object clone() + { + return new CTR(this); + } + + // Implementation of abstract methods in BaseMode + // ------------------------------------------------------------------------- + + public void setup() + { + if (modeBlockSize > cipherBlockSize) + { + throw new IllegalArgumentException( + "mode size exceeds cipher block size"); + } + off = 0; + counter = new byte[cipherBlockSize]; + int i = cipherBlockSize - 1; + int j = iv.length - 1; + while (i >= 0 && j >= 0) + { + counter[i--] = iv[j--]; + } + enc = new byte[cipherBlockSize]; + cipher.encryptBlock(counter, 0, enc, 0); + // if (modeBlockSize != cipherBlockSize) { + // throw new IllegalArgumentException(); + // } + + // byte[] tBytes = new byte[modeBlockSize+1]; + // tBytes[0] = (byte) 0x80; + // for (int i = 0; i < modeBlockSize; i++) { + // tBytes[i+1] = (byte)(256 - modeBlockSize + i); + // } + + // T = new BigInteger(1, tBytes); + } + + public void teardown() + { + if (counter != null) + { + Arrays.fill(counter, (byte) 0); + } + if (enc != null) + { + Arrays.fill(enc, (byte) 0); + } + // T = null; + } + + public void encryptBlock(byte[] in, int i, byte[] out, int o) + { + ctr(in, i, out, o); + } + + public void decryptBlock(byte[] in, int i, byte[] out, int o) + { + ctr(in, i, out, o); + } + + public Iterator blockSizes() + { + return new Sequence(1, cipherBlockSize).iterator(); + } + + // own methods + // ------------------------------------------------------------------------- + + private void ctr(byte[] in, int inOffset, byte[] out, int outOffset) + { + // T = T.add(BigInteger.ONE); + // byte[] O = T.toByteArray(); + // int ndx = O.length - modeBlockSize; + // cipher.encryptBlock(O, ndx, O, ndx); + // for (int i = 0; i < modeBlockSize; i++) { + // out[outOffset++] = (byte)(in[inOffset++] ^ O[ndx++]); + // } + for (int i = 0; i < modeBlockSize; i++) + { + out[outOffset++] = (byte) (in[inOffset++] ^ enc[off++]); + if (off == cipherBlockSize) + { + int j; + for (j = cipherBlockSize - 1; j >= 0; j--) + { + counter[j]++; + if ((counter[j] & 0xFF) != 0) + { + break; + } + } + if (j == 0) + { + counter[cipherBlockSize - 1]++; + } + off = 0; + cipher.encryptBlock(counter, 0, enc, 0); + } + } + } +}
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