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Diffstat (limited to 'core/src/main/java/org/spongycastle/crypto/modes/CFBBlockCipher.java')
| -rw-r--r-- | core/src/main/java/org/spongycastle/crypto/modes/CFBBlockCipher.java | 269 |
1 files changed, 269 insertions, 0 deletions
diff --git a/core/src/main/java/org/spongycastle/crypto/modes/CFBBlockCipher.java b/core/src/main/java/org/spongycastle/crypto/modes/CFBBlockCipher.java new file mode 100644 index 00000000..52bf2cc9 --- /dev/null +++ b/core/src/main/java/org/spongycastle/crypto/modes/CFBBlockCipher.java @@ -0,0 +1,269 @@ +package org.spongycastle.crypto.modes; + +import org.spongycastle.crypto.BlockCipher; +import org.spongycastle.crypto.CipherParameters; +import org.spongycastle.crypto.DataLengthException; +import org.spongycastle.crypto.StreamBlockCipher; +import org.spongycastle.crypto.params.ParametersWithIV; +import org.spongycastle.util.Arrays; + +/** + * implements a Cipher-FeedBack (CFB) mode on top of a simple cipher. + */ +public class CFBBlockCipher + extends StreamBlockCipher +{ + private byte[] IV; + private byte[] cfbV; + private byte[] cfbOutV; + private byte[] inBuf; + + private int blockSize; + private BlockCipher cipher = null; + private boolean encrypting; + private int byteCount; + + /** + * Basic constructor. + * + * @param cipher the block cipher to be used as the basis of the + * feedback mode. + * @param bitBlockSize the block size in bits (note: a multiple of 8) + */ + public CFBBlockCipher( + BlockCipher cipher, + int bitBlockSize) + { + super(cipher); + + this.cipher = cipher; + this.blockSize = bitBlockSize / 8; + + this.IV = new byte[cipher.getBlockSize()]; + this.cfbV = new byte[cipher.getBlockSize()]; + this.cfbOutV = new byte[cipher.getBlockSize()]; + this.inBuf = new byte[blockSize]; + } + + /** + * Initialise the cipher and, possibly, the initialisation vector (IV). + * If an IV isn't passed as part of the parameter, the IV will be all zeros. + * An IV which is too short is handled in FIPS compliant fashion. + * + * @param encrypting if true the cipher is initialised for + * encryption, if false for decryption. + * @param params the key and other data required by the cipher. + * @exception IllegalArgumentException if the params argument is + * inappropriate. + */ + public void init( + boolean encrypting, + CipherParameters params) + throws IllegalArgumentException + { + this.encrypting = encrypting; + + if (params instanceof ParametersWithIV) + { + ParametersWithIV ivParam = (ParametersWithIV)params; + byte[] iv = ivParam.getIV(); + + if (iv.length < IV.length) + { + // prepend the supplied IV with zeros (per FIPS PUB 81) + System.arraycopy(iv, 0, IV, IV.length - iv.length, iv.length); + for (int i = 0; i < IV.length - iv.length; i++) + { + IV[i] = 0; + } + } + else + { + System.arraycopy(iv, 0, IV, 0, IV.length); + } + + reset(); + + // if null it's an IV changed only. + if (ivParam.getParameters() != null) + { + cipher.init(true, ivParam.getParameters()); + } + } + else + { + reset(); + + // if it's null, key is to be reused. + if (params != null) + { + cipher.init(true, params); + } + } + } + + /** + * return the algorithm name and mode. + * + * @return the name of the underlying algorithm followed by "/CFB" + * and the block size in bits. + */ + public String getAlgorithmName() + { + return cipher.getAlgorithmName() + "/CFB" + (blockSize * 8); + } + + protected byte calculateByte(byte in) + throws DataLengthException, IllegalStateException + { + return (encrypting) ? encryptByte(in) : decryptByte(in); + } + + private byte encryptByte(byte in) + { + if (byteCount == 0) + { + cipher.processBlock(cfbV, 0, cfbOutV, 0); + } + + byte rv = (byte)(cfbOutV[byteCount] ^ in); + inBuf[byteCount++] = rv; + + if (byteCount == blockSize) + { + byteCount = 0; + + System.arraycopy(cfbV, blockSize, cfbV, 0, cfbV.length - blockSize); + System.arraycopy(inBuf, 0, cfbV, cfbV.length - blockSize, blockSize); + } + + return rv; + } + + private byte decryptByte(byte in) + { + if (byteCount == 0) + { + cipher.processBlock(cfbV, 0, cfbOutV, 0); + } + + inBuf[byteCount] = in; + byte rv = (byte)(cfbOutV[byteCount++] ^ in); + + if (byteCount == blockSize) + { + byteCount = 0; + + System.arraycopy(cfbV, blockSize, cfbV, 0, cfbV.length - blockSize); + System.arraycopy(inBuf, 0, cfbV, cfbV.length - blockSize, blockSize); + } + + return rv; + } + + /** + * return the block size we are operating at. + * + * @return the block size we are operating at (in bytes). + */ + public int getBlockSize() + { + return blockSize; + } + + /** + * Process one block of input from the array in and write it to + * the out array. + * + * @param in the array containing the input data. + * @param inOff offset into the in array the data starts at. + * @param out the array the output data will be copied into. + * @param outOff the offset into the out array the output will start at. + * @exception DataLengthException if there isn't enough data in in, or + * space in out. + * @exception IllegalStateException if the cipher isn't initialised. + * @return the number of bytes processed and produced. + */ + public int processBlock( + byte[] in, + int inOff, + byte[] out, + int outOff) + throws DataLengthException, IllegalStateException + { + processBytes(in, inOff, blockSize, out, outOff); + + return blockSize; + } + + /** + * Do the appropriate processing for CFB mode encryption. + * + * @param in the array containing the data to be encrypted. + * @param inOff offset into the in array the data starts at. + * @param out the array the encrypted data will be copied into. + * @param outOff the offset into the out array the output will start at. + * @exception DataLengthException if there isn't enough data in in, or + * space in out. + * @exception IllegalStateException if the cipher isn't initialised. + * @return the number of bytes processed and produced. + */ + public int encryptBlock( + byte[] in, + int inOff, + byte[] out, + int outOff) + throws DataLengthException, IllegalStateException + { + processBytes(in, inOff, blockSize, out, outOff); + + return blockSize; + } + + /** + * Do the appropriate processing for CFB mode decryption. + * + * @param in the array containing the data to be decrypted. + * @param inOff offset into the in array the data starts at. + * @param out the array the encrypted data will be copied into. + * @param outOff the offset into the out array the output will start at. + * @exception DataLengthException if there isn't enough data in in, or + * space in out. + * @exception IllegalStateException if the cipher isn't initialised. + * @return the number of bytes processed and produced. + */ + public int decryptBlock( + byte[] in, + int inOff, + byte[] out, + int outOff) + throws DataLengthException, IllegalStateException + { + processBytes(in, inOff, blockSize, out, outOff); + + return blockSize; + } + + /** + * Return the current state of the initialisation vector. + * + * @return current IV + */ + public byte[] getCurrentIV() + { + return Arrays.clone(cfbV); + } + + /** + * reset the chaining vector back to the IV and reset the underlying + * cipher. + */ + public void reset() + { + System.arraycopy(IV, 0, cfbV, 0, IV.length); + Arrays.fill(inBuf, (byte)0); + byteCount = 0; + + cipher.reset(); + } +} |