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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 to JDK 1.8.

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package org.bouncycastle.crypto.macs;

import org.bouncycastle.crypto.BlockCipher;
import org.bouncycastle.crypto.CipherParameters;
import org.bouncycastle.crypto.Mac;
import org.bouncycastle.crypto.modes.CBCBlockCipher;

public class BlockCipherMac
    implements Mac
{
    private byte[]          mac;

    private byte[]          buf;
    private int             bufOff;
    private BlockCipher     cipher;

    private int             macSize;

    /**
     * create a standard MAC based on a block cipher. This will produce an
     * authentication code half the length of the block size of the cipher.
     *
     * @param cipher the cipher to be used as the basis of the MAC generation.
     * @deprecated use CBCBlockCipherMac
     */
    public BlockCipherMac(
        BlockCipher     cipher)
    {
        this(cipher, (cipher.getBlockSize() * 8) / 2);
    }

    /**
     * create a standard MAC based on a block cipher with the size of the
     * MAC been given in bits.
     * 

* Note: the size of the MAC must be at least 16 bits (FIPS Publication 113), * and in general should be less than the size of the block cipher as it reduces * the chance of an exhaustive attack (see Handbook of Applied Cryptography). * * @param cipher the cipher to be used as the basis of the MAC generation. * @param macSizeInBits the size of the MAC in bits, must be a multiple of 8. * @deprecated use CBCBlockCipherMac */ public BlockCipherMac( BlockCipher cipher, int macSizeInBits) { if ((macSizeInBits % 8) != 0) { throw new IllegalArgumentException("MAC size must be multiple of 8"); } this.cipher = new CBCBlockCipher(cipher); this.macSize = macSizeInBits / 8; mac = new byte[cipher.getBlockSize()]; buf = new byte[cipher.getBlockSize()]; bufOff = 0; } public String getAlgorithmName() { return cipher.getAlgorithmName(); } public void init( CipherParameters params) { reset(); cipher.init(true, params); } public int getMacSize() { return macSize; } public void update( byte in) { if (bufOff == buf.length) { cipher.processBlock(buf, 0, mac, 0); bufOff = 0; } buf[bufOff++] = in; } public void update( byte[] in, int inOff, int len) { if (len < 0) { throw new IllegalArgumentException("Can't have a negative input length!"); } int blockSize = cipher.getBlockSize(); int resultLen = 0; int gapLen = blockSize - bufOff; if (len > gapLen) { System.arraycopy(in, inOff, buf, bufOff, gapLen); resultLen += cipher.processBlock(buf, 0, mac, 0); bufOff = 0; len -= gapLen; inOff += gapLen; while (len > blockSize) { resultLen += cipher.processBlock(in, inOff, mac, 0); len -= blockSize; inOff += blockSize; } } System.arraycopy(in, inOff, buf, bufOff, len); bufOff += len; } public int doFinal( byte[] out, int outOff) { int blockSize = cipher.getBlockSize(); // // pad with zeroes // while (bufOff < blockSize) { buf[bufOff] = 0; bufOff++; } cipher.processBlock(buf, 0, mac, 0); System.arraycopy(mac, 0, out, outOff, macSize); reset(); return macSize; } /** * Reset the mac generator. */ public void reset() { /* * clean the buffer. */ for (int i = 0; i < buf.length; i++) { buf[i] = 0; } bufOff = 0; /* * reset the underlying cipher. */ cipher.reset(); } }





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