/**
* create a standard MAC based on a block cipher with the size of the
* MAC been given in bits. This class uses CFB mode as the basis for the
* MAC generation.
* <p>
* Note: the size of the MAC must be at least 24 bits (FIPS Publication 81),
* or 16 bits if being used as a data authenticator (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).
* </p>
* @param cipher the cipher to be used as the basis of the MAC generation.
* @param cfbBitSize the size of an output block produced by the CFB mode.
* @param macSizeInBits the size of the MAC in bits, must be a multiple of 8.
* @param padding a padding to be used.
*/
public CfbBlockCipherMac(
IBlockCipher cipher,
int cfbBitSize,
int macSizeInBits,
IBlockCipherPadding padding)
{
if ((macSizeInBits % 8) != 0)
{
throw new ArgumentException("MAC size must be multiple of 8");
}
mac = new byte[cipher.GetBlockSize()];
this.cipher = new MacCFBBlockCipher(cipher, cfbBitSize);
this.padding = padding;
this.macSize = macSizeInBits / 8;
Buffer = new byte[this.cipher.GetBlockSize()];
bufOff = 0;
}
/**
* create a standard MAC based on a block cipher with the size of the
* MAC been given in bits. This class uses CFB mode as the basis for the
* MAC generation.
* <p>
* Note: the size of the MAC must be at least 24 bits (FIPS Publication 81),
* or 16 bits if being used as a data authenticator (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).
* </p>
* @param cipher the cipher to be used as the basis of the MAC generation.
* @param cfbBitSize the size of an output block produced by the CFB mode.
* @param macSizeInBits the size of the MAC in bits, must be a multiple of 8.
* @param padding a padding to be used.
*/
public CfbBlockCipherMac(
IBlockCipher cipher,
int cfbBitSize,
int macSizeInBits,
IBlockCipherPadding padding)
{
if ((macSizeInBits % 8) != 0)
throw new ArgumentException("MAC size must be multiple of 8");
mac = new byte[cipher.GetBlockSize()];
this.cipher = new MacCFBBlockCipher(cipher, cfbBitSize);
this.padding = padding;
this.macSize = macSizeInBits / 8;
Buffer = new byte[this.cipher.GetBlockSize()];
bufOff = 0;
}