| /* GENERATED SOURCE. DO NOT MODIFY. */ |
| package com.android.org.bouncycastle.crypto.modes; |
| |
| import com.android.org.bouncycastle.crypto.BlockCipher; |
| import com.android.org.bouncycastle.crypto.CipherParameters; |
| import com.android.org.bouncycastle.crypto.DataLengthException; |
| import com.android.org.bouncycastle.crypto.params.ParametersWithIV; |
| import com.android.org.bouncycastle.util.Arrays; |
| |
| /** |
| * implements Cipher-Block-Chaining (CBC) mode on top of a simple cipher. |
| * @hide This class is not part of the Android public SDK API |
| */ |
| public class CBCBlockCipher |
| implements BlockCipher |
| { |
| private byte[] IV; |
| private byte[] cbcV; |
| private byte[] cbcNextV; |
| |
| private int blockSize; |
| private BlockCipher cipher = null; |
| private boolean encrypting; |
| |
| /** |
| * Basic constructor. |
| * |
| * @param cipher the block cipher to be used as the basis of chaining. |
| */ |
| public CBCBlockCipher( |
| BlockCipher cipher) |
| { |
| this.cipher = cipher; |
| this.blockSize = cipher.getBlockSize(); |
| |
| this.IV = new byte[blockSize]; |
| this.cbcV = new byte[blockSize]; |
| this.cbcNextV = new byte[blockSize]; |
| } |
| |
| /** |
| * return the underlying block cipher that we are wrapping. |
| * |
| * @return the underlying block cipher that we are wrapping. |
| */ |
| public BlockCipher getUnderlyingCipher() |
| { |
| return cipher; |
| } |
| |
| /** |
| * 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 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 |
| { |
| boolean oldEncrypting = this.encrypting; |
| |
| 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(); |
| |
| // if null it's an IV changed only. |
| if (ivParam.getParameters() != null) |
| { |
| cipher.init(encrypting, ivParam.getParameters()); |
| } |
| else if (oldEncrypting != encrypting) |
| { |
| throw new IllegalArgumentException("cannot change encrypting state without providing key."); |
| } |
| } |
| else |
| { |
| reset(); |
| |
| // if it's null, key is to be reused. |
| if (params != null) |
| { |
| cipher.init(encrypting, params); |
| } |
| else if (oldEncrypting != encrypting) |
| { |
| throw new IllegalArgumentException("cannot change encrypting state without providing key."); |
| } |
| } |
| } |
| |
| /** |
| * return the algorithm name and mode. |
| * |
| * @return the name of the underlying algorithm followed by "/CBC". |
| */ |
| public String getAlgorithmName() |
| { |
| return cipher.getAlgorithmName() + "/CBC"; |
| } |
| |
| /** |
| * return the block size of the underlying cipher. |
| * |
| * @return the block size of the underlying cipher. |
| */ |
| public int getBlockSize() |
| { |
| return cipher.getBlockSize(); |
| } |
| |
| /** |
| * 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 |
| { |
| return (encrypting) ? encryptBlock(in, inOff, out, outOff) : decryptBlock(in, inOff, out, outOff); |
| } |
| |
| /** |
| * reset the chaining vector back to the IV and reset the underlying |
| * cipher. |
| */ |
| public void reset() |
| { |
| System.arraycopy(IV, 0, cbcV, 0, IV.length); |
| Arrays.fill(cbcNextV, (byte)0); |
| |
| cipher.reset(); |
| } |
| |
| /** |
| * 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. |
| */ |
| private int encryptBlock( |
| byte[] in, |
| int inOff, |
| byte[] out, |
| int outOff) |
| throws DataLengthException, IllegalStateException |
| { |
| 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; |
| } |
| |
| /** |
| * 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. |
| */ |
| private int decryptBlock( |
| byte[] in, |
| int inOff, |
| byte[] out, |
| int outOff) |
| throws DataLengthException, IllegalStateException |
| { |
| 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; |
| } |
| } |