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src/Cryptography/CBC.cpp 9e0fb0258103d1bab3e0e4cf812db1506928bbb6 (9e0fb025) Text, 4.59 KB
/*
* Copyright (C) 2015 Southern Storm Software, Pty Ltd.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
#include "CBC.h"
#include "Crypto.h"
#include <string.h>
/**
* \\class CBCCommon CBC.h <CBC.h>
* \\brief Concrete base class to assist with implementing CBC for
* 128-bit block ciphers.
*
* Reference: http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation
*
* \\sa CBC
*/
/**
* \\brief Constructs a new cipher in CBC mode.
*
* This constructor should be followed by a call to setBlockCipher().
*/
CBCCommon::CBCCommon()
: blockCipher(0)
, posn(16)
{
}
/**
* \\brief Destroys this cipher object after clearing sensitive information.
*/
CBCCommon::~CBCCommon()
{
clean(iv);
clean(temp);
}
size_t CBCCommon::keySize() const
{
return blockCipher->keySize();
}
size_t CBCCommon::ivSize() const
{
return 16;
}
bool CBCCommon::setKey(const uint8_t* key, size_t len)
{
// Verify the cipher's block size, just in case.
if (blockCipher->blockSize() != 16)
return false;
// Set the key on the underlying block cipher.
return blockCipher->setKey(key, len);
}
bool CBCCommon::setIV(const uint8_t* iv, size_t len)
{
if (len != 16)
return false;
memcpy(this->iv, iv, 16);
posn = 16;
return true;
}
void CBCCommon::encrypt(uint8_t* output, const uint8_t* input, size_t len)
{
uint8_t posn;
while (len >= 16) {
for (posn = 0; posn < 16; ++posn)
iv[posn] ^= *input++;
blockCipher->encryptBlock(iv, iv);
for (posn = 0; posn < 16; ++posn)
*output++ = iv[posn];
len -= 16;
}
}
void CBCCommon::decrypt(uint8_t* output, const uint8_t* input, size_t len)
{
uint8_t posn;
while (len >= 16) {
blockCipher->decryptBlock(temp, input);
for (posn = 0; posn < 16; ++posn) {
uint8_t in = *input++;
*output++ = temp[posn] ^ iv[posn];
iv[posn] = in;
}
len -= 16;
}
}
void CBCCommon::clear()
{
blockCipher->clear();
clean(iv);
clean(temp);
posn = 16;
}
/**
* \\fn void CBCCommon::setBlockCipher(BlockCipher *cipher)
* \\brief Sets the block cipher to use for this CBC object.
*
* \\param cipher The block cipher to use to implement CBC mode,
* which must have a block size of 16 bytes (128 bits).
*/
/**
* \\class CBC CBC.h <CBC.h>
* \\brief Implementation of the Cipher Block Chaining (CBC) mode for
* 128-bit block ciphers.
*
* The template parameter T must be a concrete subclass of BlockCipher
* indicating the specific block cipher to use. T must have a block size
* of 16 bytes (128 bits).
*
* For example, the following creates a CBC object using AES192 as the
* underlying cipher:
*
* \\code
* CBC<AES192> cbc;
* cbc.setKey(key, 24);
* cbc.setIV(iv, 16);
* cbc.encrypt(output, input, len);
* \\endcode
*
* Decryption is similar:
*
* \\code
* CBC<AES192> cbc;
* cbc.setKey(key, 24);
* cbc.setIV(iv, 16);
* cbc.decrypt(output, input, len);
* \\endcode
*
* The size of the ciphertext will always be the same as the size of
* the plaintext. Also, the length of the plaintext/ciphertext must be a
* multiple of 16. Extra bytes are ignored and not encrypted. The caller
* is responsible for padding the underlying data to a multiple of 16
* using an appropriate padding scheme for the application.
*
* Reference: http://en.wikipedia.org/wiki/Block_cipher_mode_of_operation
*
* \\sa CTR, CFB, OFB
*/
/**
* \\fn CBC::CBC()
* \\brief Constructs a new CBC object for the block cipher T.
*/
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