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/*
* CTS Mode
* (C) 1999-2007 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/cts.h>
#include <botan/xor_buf.h>
#include <algorithm>
namespace Botan {
/*
* Encrypt a block
*/
void CTS_Encryption::encrypt(const byte block[])
{
xor_buf(state, block, BLOCK_SIZE);
cipher->encrypt(state);
send(state, BLOCK_SIZE);
}
/*
* Encrypt in CTS mode
*/
void CTS_Encryption::write(const byte input[], u32bit length)
{
u32bit copied = std::min(BUFFER_SIZE - position, length);
buffer.copy(position, input, copied);
length -= copied;
input += copied;
position += copied;
if(length == 0) return;
encrypt(buffer);
if(length > BLOCK_SIZE)
{
encrypt(buffer + BLOCK_SIZE);
while(length > 2*BLOCK_SIZE)
{
encrypt(input);
length -= BLOCK_SIZE;
input += BLOCK_SIZE;
}
position = 0;
}
else
{
copy_mem(buffer.begin(), buffer + BLOCK_SIZE, BLOCK_SIZE);
position = BLOCK_SIZE;
}
buffer.copy(position, input, length);
position += length;
}
/*
* Finish encrypting in CTS mode
*/
void CTS_Encryption::end_msg()
{
if(position < BLOCK_SIZE + 1)
throw Exception("CTS_Encryption: insufficient data to encrypt");
xor_buf(state, buffer, BLOCK_SIZE);
cipher->encrypt(state);
SecureVector<byte> cn = state;
clear_mem(buffer + position, BUFFER_SIZE - position);
encrypt(buffer + BLOCK_SIZE);
send(cn, position - BLOCK_SIZE);
}
/*
* Decrypt a block
*/
void CTS_Decryption::decrypt(const byte block[])
{
cipher->decrypt(block, temp);
xor_buf(temp, state, BLOCK_SIZE);
send(temp, BLOCK_SIZE);
state.copy(block, BLOCK_SIZE);
}
/*
* Decrypt in CTS mode
*/
void CTS_Decryption::write(const byte input[], u32bit length)
{
u32bit copied = std::min(BUFFER_SIZE - position, length);
buffer.copy(position, input, copied);
length -= copied;
input += copied;
position += copied;
if(length == 0) return;
decrypt(buffer);
if(length > BLOCK_SIZE)
{
decrypt(buffer + BLOCK_SIZE);
while(length > 2*BLOCK_SIZE)
{
decrypt(input);
length -= BLOCK_SIZE;
input += BLOCK_SIZE;
}
position = 0;
}
else
{
copy_mem(buffer.begin(), buffer + BLOCK_SIZE, BLOCK_SIZE);
position = BLOCK_SIZE;
}
buffer.copy(position, input, length);
position += length;
}
/*
* Finish decrypting in CTS mode
*/
void CTS_Decryption::end_msg()
{
cipher->decrypt(buffer, temp);
xor_buf(temp, buffer + BLOCK_SIZE, position - BLOCK_SIZE);
SecureVector<byte> xn = temp;
copy_mem(buffer + position, xn + (position - BLOCK_SIZE),
BUFFER_SIZE - position);
cipher->decrypt(buffer + BLOCK_SIZE, temp);
xor_buf(temp, state, BLOCK_SIZE);
send(temp, BLOCK_SIZE);
send(xn, position - BLOCK_SIZE);
}
}
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