File	Doc	Category	Size	Date	Package
CBCBlockCipher.java	API Doc	Azureus 3.0.3.4	6856	Tue Jun 08 05:12:58 BST 2004	org.bouncycastle.crypto.modes

CBCBlockCipher

• java.lang.Object

Fields Summary
private byte[]	IV
private byte[]	cbcV
private byte[]	cbcNextV
private int	blockSize
private org.bouncycastle.crypto.BlockCipher	cipher
private boolean	encrypting

Constructors Summary
public CBCBlockCipher(org.bouncycastle.crypto.BlockCipher cipher) Basic constructor. param cipher the block cipher to be used as the basis of chaining. this.cipher = cipher; this.blockSize = cipher.getBlockSize(); this.IV = new byte[blockSize]; this.cbcV = new byte[blockSize]; this.cbcNextV = new byte[blockSize];

Methods Summary
private int	decryptBlock(byte[] in, int inOff, byte[] out, int outOff) Do the appropriate chaining step for CBC 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 decrypted 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. if ((inOff + blockSize) > in.length) { throw new DataLengthException("input buffer too short"); } System.arraycopy(in, inOff, cbcNextV, 0, blockSize); int length = cipher.processBlock(in, inOff, out, outOff); /* * XOR the cbcV and the output */ for (int i = 0; i < blockSize; i++) { out[outOff + i] ^= cbcV[i]; } /* * swap the back up buffer into next position */ byte[] tmp; tmp = cbcV; cbcV = cbcNextV; cbcNextV = tmp; return length;
private int	encryptBlock(byte[] in, int inOff, byte[] out, int outOff) Do the appropriate chaining step for CBC 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. if ((inOff + blockSize) > in.length) { throw new DataLengthException("input buffer too short"); } /* * XOR the cbcV and the input, * then encrypt the cbcV */ for (int i = 0; i < blockSize; i++) { cbcV[i] ^= in[inOff + i]; } int length = cipher.processBlock(cbcV, 0, out, outOff); /* * copy ciphertext to cbcV */ System.arraycopy(out, outOff, cbcV, 0, cbcV.length); return length;
public java.lang.String	getAlgorithmName() return the algorithm name and mode. return the name of the underlying algorithm followed by "/CBC". return cipher.getAlgorithmName() + "/CBC";
public int	getBlockSize() return the block size of the underlying cipher. return the block size of the underlying cipher. return cipher.getBlockSize();
public org.bouncycastle.crypto.BlockCipher	getUnderlyingCipher() return the underlying block cipher that we are wrapping. return the underlying block cipher that we are wrapping. return cipher;
public void	init(boolean encrypting, org.bouncycastle.crypto.CipherParameters params) 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. param forEncryption if true the cipher is initialised for encryption, if false for decryption. param param the key and other data required by the cipher. exception IllegalArgumentException if the params argument is inappropriate. this.encrypting = encrypting; if (params instanceof ParametersWithIV) { ParametersWithIV ivParam = (ParametersWithIV)params; byte[] iv = ivParam.getIV(); if (iv.length != blockSize) { throw new IllegalArgumentException("initialisation vector must be the same length as block size"); } System.arraycopy(iv, 0, IV, 0, iv.length); reset(); cipher.init(encrypting, ivParam.getParameters()); } else { reset(); cipher.init(encrypting, params); }
public int	processBlock(byte[] in, int inOff, byte[] out, int outOff) 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. return (encrypting) ? encryptBlock(in, inOff, out, outOff) : decryptBlock(in, inOff, out, outOff);
public void	reset() reset the chaining vector back to the IV and reset the underlying cipher. System.arraycopy(IV, 0, cbcV, 0, IV.length); cipher.reset();