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/*************************************************
* CTR Mode Source File *
* (C) 1999-2007 Jack Lloyd *
*************************************************/
#include <botan/ctr.h>
#include <botan/lookup.h>
#include <botan/bit_ops.h>
#include <algorithm>
namespace Botan {
/*************************************************
* CTR-BE Constructor *
*************************************************/
CTR_BE::CTR_BE(const std::string& cipher_name) :
BlockCipherMode(cipher_name, "CTR-BE", block_size_of(cipher_name), 1)
{
}
/*************************************************
* CTR-BE Constructor *
*************************************************/
CTR_BE::CTR_BE(const std::string& cipher_name, const SymmetricKey& key,
const InitializationVector& iv) :
BlockCipherMode(cipher_name, "CTR-BE", block_size_of(cipher_name), 1)
{
set_key(key);
set_iv(iv);
}
/*************************************************
* CTR-BE Encryption/Decryption *
*************************************************/
void CTR_BE::write(const byte input[], u32bit length)
{
u32bit copied = std::min(BLOCK_SIZE - position, length);
xor_buf(buffer + position, input, copied);
send(buffer + position, copied);
input += copied;
length -= copied;
position += copied;
if(position == BLOCK_SIZE)
increment_counter();
while(length >= BLOCK_SIZE)
{
xor_buf(buffer, input, BLOCK_SIZE);
send(buffer, BLOCK_SIZE);
input += BLOCK_SIZE;
length -= BLOCK_SIZE;
increment_counter();
}
xor_buf(buffer + position, input, length);
send(buffer + position, length);
position += length;
}
/*************************************************
* Increment the counter and update the buffer *
*************************************************/
void CTR_BE::increment_counter()
{
for(s32bit j = BLOCK_SIZE - 1; j >= 0; --j)
if(++state[j])
break;
cipher->encrypt(state, buffer);
position = 0;
}
}
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