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Diffstat (limited to 'gnu/javax/crypto/prng/ICMGenerator.java')
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diff --git a/gnu/javax/crypto/prng/ICMGenerator.java b/gnu/javax/crypto/prng/ICMGenerator.java new file mode 100644 index 000000000..0de38e256 --- /dev/null +++ b/gnu/javax/crypto/prng/ICMGenerator.java @@ -0,0 +1,379 @@ +/* ICMGenerator.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.prng; + +import gnu.java.security.Registry; +import gnu.java.security.prng.BasePRNG; +import gnu.java.security.prng.LimitReachedException; + +import gnu.javax.crypto.cipher.IBlockCipher; +import gnu.javax.crypto.cipher.CipherFactory; + +import java.math.BigInteger; +import java.security.InvalidKeyException; +import java.util.HashMap; +import java.util.Map; + +/** + * <p>Counter Mode is a way to define a pseudorandom keystream generator using + * a block cipher. The keystream can be used for additive encryption, key + * derivation, or any other application requiring pseudorandom data.</p> + * + * <p>In ICM, the keystream is logically broken into segments. Each segment is + * identified with a segment index, and the segments have equal lengths. This + * segmentation makes ICM especially appropriate for securing packet-based + * protocols.</p> + * + * <p>This implementation adheres to the definition of the ICM keystream + * generation function that allows for any symetric key block cipher algorithm + * (initialisation parameter <code>gnu.crypto.prng.icm.cipher.name</code> taken + * to be an instance of {@link java.lang.String}) to be used. If such a + * parameter is not defined/included in the initialisation <code>Map</code>, + * then the "Rijndael" algorithm is used. Furthermore, if the initialisation + * parameter <code>gnu.crypto.cipher.block.size</code> (taken to be a instance + * of {@link java.lang.Integer}) is missing or undefined in the initialisation + * <code>Map</code>, then the cipher's <em>default</em> block size is used.</p> + * + * <p>The practical limits and constraints of such generator are:</p> + * <ul> + * <li>The number of blocks in any segment <b>MUST NOT</b> exceed <code> + * 256 ** BLOCK_INDEX_LENGTH</code>. The number of segments <b>MUST NOT</b> + * exceed <code>256 ** SEGMENT_INDEX_LENGTH</code>. These restrictions ensure + * the uniqueness of each block cipher input.</li> + * + * <li>Each segment contains <code>SEGMENT_LENGTH</code> octets; this value + * <b>MUST NOT</b> exceed the value <code>(256 ** BLOCK_INDEX_LENGTH) * + * BLOCK_LENGTH</code>.</li> + * + * <li>The sum of <code>SEGMENT_INDEX_LENGTH</code> and + * <code>BLOCK_INDEX_LENGTH</code> <b>MUST NOT</b> exceed <code>BLOCK_LENGTH + * / 2</code>. This requirement protects the ICM keystream generator from + * potentially failing to be pseudorandom.</li> + * </ul> + * + * <p><b>NOTE</b>: Rijndael is used as the default symmetric key block cipher + * algorithm because, with its default block and key sizes, it is the AES. Yet + * being Rijndael, the algorithm offers more versatile block and key sizes which + * may prove to be useful for generating <em>longer</em> key streams.</p> + * + * <p>References:</p> + * + * <ol> + * <li><a href="http://www.ietf.org/internet-drafts/draft-mcgrew-saag-icm-00.txt"> + * Integer Counter Mode</a>, David A. McGrew.</li> + * </ol> + * + * @version $Revision: 1.1 $ + */ +public class ICMGenerator extends BasePRNG implements Cloneable +{ + + // Constants and variables + // ------------------------------------------------------------------------- + + /** Property name of underlying block cipher for this ICM generator. */ + public static final String CIPHER = "gnu.crypto.prng.icm.cipher.name"; + + /** Property name of ICM's block index length. */ + public static final String BLOCK_INDEX_LENGTH = "gnu.crypto.prng.icm.block.index.length"; + + /** Property name of ICM's segment index length. */ + public static final String SEGMENT_INDEX_LENGTH = "gnu.crypto.prng.icm.segment.index.length"; + + /** Property name of ICM's offset. */ + public static final String OFFSET = "gnu.crypto.prng.icm.offset"; + + /** Property name of ICM's segment index. */ + public static final String SEGMENT_INDEX = "gnu.crypto.prng.icm.segment.index"; + + /** The integer value 256 as a BigInteger. */ + private static final BigInteger TWO_FIFTY_SIX = new BigInteger("256"); + + /** The underlying cipher implementation. */ + private IBlockCipher cipher; + + /** This keystream block index length in bytes. */ + private int blockNdxLength = -1; + + /** This keystream segment index length in bytes. */ + private int segmentNdxLength = -1; + + /** The index of the next block for a given keystream segment. */ + private BigInteger blockNdx = BigInteger.ZERO; + + /** The segment index for this keystream. */ + private BigInteger segmentNdx; + + /** The initial counter for a given keystream segment. */ + private BigInteger C0; + + // Constructor(s) + // ------------------------------------------------------------------------- + + /** Trivial 0-arguments constructor. */ + public ICMGenerator() + { + super(Registry.ICM_PRNG); + } + + // Class methods + // ------------------------------------------------------------------------- + + // Instance methods + // ------------------------------------------------------------------------- + + // Implementation of abstract methods in BasePRNG -------------------------- + + // Conceptually, ICM is a keystream generator that takes a secret key + // and a segment index as an input and then outputs a keystream + // segment. The segmentation lends itself to packet encryption, as + // each keystream segment can be used to encrypt a distinct packet. + // + // An ICM key consists of the block cipher key and an Offset. The + // Offset is an integer with BLOCK_LENGTH octets... + // + public void setup(Map attributes) + { + // find out which cipher algorithm to use + boolean newCipher = true; + String underlyingCipher = (String) attributes.get(CIPHER); + if (underlyingCipher == null) + { + if (cipher == null) + { // happy birthday + // ensure we have a reliable implementation of this cipher + cipher = CipherFactory.getInstance(Registry.RIJNDAEL_CIPHER); + } + else + { // we already have one. use it as is + newCipher = false; + } + } + else + { // ensure we have a reliable implementation of this cipher + cipher = CipherFactory.getInstance(underlyingCipher); + } + + // find out what block size we should use it in + int cipherBlockSize = 0; + Integer bs = (Integer) attributes.get(IBlockCipher.CIPHER_BLOCK_SIZE); + if (bs != null) + { + cipherBlockSize = bs.intValue(); + } + else + { + if (newCipher) + { // assume we'll use its default block size + cipherBlockSize = cipher.defaultBlockSize(); + } // else use as is + } + + // get the key material + byte[] key = (byte[]) attributes.get(IBlockCipher.KEY_MATERIAL); + if (key == null) + { + throw new IllegalArgumentException(IBlockCipher.KEY_MATERIAL); + } + + // now initialise the cipher + HashMap map = new HashMap(); + if (cipherBlockSize != 0) + { // only needed if new or changed + map.put(IBlockCipher.CIPHER_BLOCK_SIZE, new Integer(cipherBlockSize)); + } + map.put(IBlockCipher.KEY_MATERIAL, key); + try + { + cipher.init(map); + } + catch (InvalidKeyException x) + { + throw new IllegalArgumentException(IBlockCipher.KEY_MATERIAL); + } + + // at this point we have an initialised (new or otherwise) cipher + // ensure that remaining params make sense + + cipherBlockSize = cipher.currentBlockSize(); + BigInteger counterRange = TWO_FIFTY_SIX.pow(cipherBlockSize); + + // offset, like the underlying cipher key is not cloneable + // always look for it and throw an exception if it's not there + Object obj = attributes.get(OFFSET); + // allow either a byte[] or a BigInteger + BigInteger r; + if (obj instanceof BigInteger) + { + r = (BigInteger) obj; + } + else + { // assume byte[]. should be same length as cipher block size + byte[] offset = (byte[]) obj; + if (offset.length != cipherBlockSize) + { + throw new IllegalArgumentException(OFFSET); + } + + r = new BigInteger(1, offset); + } + + int wantBlockNdxLength = -1; // number of octets in the block index + Integer i = (Integer) attributes.get(BLOCK_INDEX_LENGTH); + if (i != null) + { + wantBlockNdxLength = i.intValue(); + if (wantBlockNdxLength < 1) + { + throw new IllegalArgumentException(BLOCK_INDEX_LENGTH); + } + } + + int wantSegmentNdxLength = -1; // number of octets in the segment index + i = (Integer) attributes.get(SEGMENT_INDEX_LENGTH); + if (i != null) + { + wantSegmentNdxLength = i.intValue(); + if (wantSegmentNdxLength < 1) + { + throw new IllegalArgumentException(SEGMENT_INDEX_LENGTH); + } + } + + // if both are undefined check if it's a reuse + if ((wantBlockNdxLength == -1) && (wantSegmentNdxLength == -1)) + { + if (blockNdxLength == -1) + { // new instance + throw new IllegalArgumentException(BLOCK_INDEX_LENGTH + ", " + + SEGMENT_INDEX_LENGTH); + } // else reuse old values + } + else + { // only one is undefined, set it to BLOCK_LENGTH/2 minus the other + int limit = cipherBlockSize / 2; + if (wantBlockNdxLength == -1) + { + wantBlockNdxLength = limit - wantSegmentNdxLength; + } + else if (wantSegmentNdxLength == -1) + { + wantSegmentNdxLength = limit - wantBlockNdxLength; + } + else if ((wantSegmentNdxLength + wantBlockNdxLength) > limit) + { + throw new IllegalArgumentException(BLOCK_INDEX_LENGTH + ", " + + SEGMENT_INDEX_LENGTH); + } + // save new values + blockNdxLength = wantBlockNdxLength; + segmentNdxLength = wantSegmentNdxLength; + } + + // get the segment index as a BigInteger + BigInteger s = (BigInteger) attributes.get(SEGMENT_INDEX); + if (s == null) + { + if (segmentNdx == null) + { // segment index was never set + throw new IllegalArgumentException(SEGMENT_INDEX); + } + // reuse; check if still valid + if (segmentNdx.compareTo(TWO_FIFTY_SIX.pow(segmentNdxLength)) > 0) + { + throw new IllegalArgumentException(SEGMENT_INDEX); + } + } + else + { + if (s.compareTo(TWO_FIFTY_SIX.pow(segmentNdxLength)) > 0) + { + throw new IllegalArgumentException(SEGMENT_INDEX); + } + segmentNdx = s; + } + + // The initial counter of the keystream segment with segment index s is + // defined as follows, where r denotes the Offset: + // + // C[0] = (s * (256^BLOCK_INDEX_LENGTH) + r) modulo (256^BLOCK_LENGTH) + // + C0 = segmentNdx.multiply(TWO_FIFTY_SIX.pow(blockNdxLength)).add(r).modPow( + BigInteger.ONE, + counterRange); + } + + public void fillBlock() throws LimitReachedException + { + if (C0 == null) + { + throw new IllegalStateException(); + } + if (blockNdx.compareTo(TWO_FIFTY_SIX.pow(blockNdxLength)) >= 0) + { + throw new LimitReachedException(); + } + + int cipherBlockSize = cipher.currentBlockSize(); + BigInteger counterRange = TWO_FIFTY_SIX.pow(cipherBlockSize); + + // encrypt the counter for the current blockNdx + // C[i] = (C[0] + i) modulo (256^BLOCK_LENGTH). + + BigInteger Ci = C0.add(blockNdx).modPow(BigInteger.ONE, counterRange); + buffer = Ci.toByteArray(); + int limit = buffer.length; + if (limit < cipherBlockSize) + { + byte[] data = new byte[cipherBlockSize]; + System.arraycopy(buffer, 0, data, cipherBlockSize - limit, limit); + buffer = data; + } + else if (limit > cipherBlockSize) + { + byte[] data = new byte[cipherBlockSize]; + System.arraycopy(buffer, limit - cipherBlockSize, data, 0, + cipherBlockSize); + buffer = data; + } + + cipher.encryptBlock(buffer, 0, buffer, 0); + blockNdx = blockNdx.add(BigInteger.ONE); // increment blockNdx + } +}
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