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/*************************************************
* Salsa20 Source File *
* (C) 1999-2008 Jack Lloyd *
*************************************************/
#include <botan/salsa20.h>
#include <botan/mem_ops.h>
#include <botan/xor_buf.h>
#include <botan/loadstor.h>
#include <botan/parsing.h>
namespace Botan {
namespace {
/*************************************************
* Generate Salsa20 cipher stream *
*************************************************/
void salsa20(byte output[64], u32bit input[16])
{
u32bit x[16];
copy_mem(x, input, 16);
for(u32bit i = 0; i != 10; ++i)
{
x[ 4] ^= rotate_left(x[ 0] + x[12], 7);
x[ 8] ^= rotate_left(x[ 4] + x[ 0], 9);
x[12] ^= rotate_left(x[ 8] + x[ 4], 13);
x[ 0] ^= rotate_left(x[12] + x[ 8], 18);
x[ 9] ^= rotate_left(x[ 5] + x[ 1], 7);
x[13] ^= rotate_left(x[ 9] + x[ 5], 9);
x[ 1] ^= rotate_left(x[13] + x[ 9], 13);
x[ 5] ^= rotate_left(x[ 1] + x[13], 18);
x[14] ^= rotate_left(x[10] + x[ 6], 7);
x[ 2] ^= rotate_left(x[14] + x[10], 9);
x[ 6] ^= rotate_left(x[ 2] + x[14], 13);
x[10] ^= rotate_left(x[ 6] + x[ 2], 18);
x[ 3] ^= rotate_left(x[15] + x[11], 7);
x[ 7] ^= rotate_left(x[ 3] + x[15], 9);
x[11] ^= rotate_left(x[ 7] + x[ 3], 13);
x[15] ^= rotate_left(x[11] + x[ 7], 18);
x[ 1] ^= rotate_left(x[ 0] + x[ 3], 7);
x[ 2] ^= rotate_left(x[ 1] + x[ 0], 9);
x[ 3] ^= rotate_left(x[ 2] + x[ 1], 13);
x[ 0] ^= rotate_left(x[ 3] + x[ 2], 18);
x[ 6] ^= rotate_left(x[ 5] + x[ 4], 7);
x[ 7] ^= rotate_left(x[ 6] + x[ 5], 9);
x[ 4] ^= rotate_left(x[ 7] + x[ 6], 13);
x[ 5] ^= rotate_left(x[ 4] + x[ 7], 18);
x[11] ^= rotate_left(x[10] + x[ 9], 7);
x[ 8] ^= rotate_left(x[11] + x[10], 9);
x[ 9] ^= rotate_left(x[ 8] + x[11], 13);
x[10] ^= rotate_left(x[ 9] + x[ 8], 18);
x[12] ^= rotate_left(x[15] + x[14], 7);
x[13] ^= rotate_left(x[12] + x[15], 9);
x[14] ^= rotate_left(x[13] + x[12], 13);
x[15] ^= rotate_left(x[14] + x[13], 18);
}
for(u32bit i = 0; i != 16; ++i)
store_le(x[i] + input[i], output + 4 * i);
++input[8];
if(!input[8])
++input[9];
}
}
/*************************************************
* Combine cipher stream with message *
*************************************************/
void Salsa20::cipher(const byte in[], byte out[], u32bit length)
{
while(length >= buffer.size() - position)
{
xor_buf(out, in, buffer.begin() + position, buffer.size() - position);
length -= (buffer.size() - position);
in += (buffer.size() - position);
out += (buffer.size() - position);
salsa20(buffer.begin(), state);
position = 0;
}
xor_buf(out, in, buffer.begin() + position, length);
position += length;
}
/*************************************************
* Salsa20 Key Schedule *
*************************************************/
void Salsa20::key(const byte key[], u32bit length)
{
clear();
if(length == 16)
{
const u32bit TAU[] = { 0x61707865, 0x3120646e, 0x79622d36, 0x6b206574 };
state[0] = TAU[0];
state[1] = load_le<u32bit>(key, 0);
state[2] = load_le<u32bit>(key, 1);
state[3] = load_le<u32bit>(key, 2);
state[4] = load_le<u32bit>(key, 3);
state[5] = TAU[1];
state[10] = TAU[2];
state[11] = load_le<u32bit>(key, 0);
state[12] = load_le<u32bit>(key, 1);
state[13] = load_le<u32bit>(key, 2);
state[14] = load_le<u32bit>(key, 3);
state[15] = TAU[3];
}
else if(length == 32)
{
const u32bit SIGMA[] = { 0x61707865, 0x3320646e, 0x79622d32, 0x6b206574 };
state[0] = SIGMA[0];
state[1] = load_le<u32bit>(key, 0);
state[2] = load_le<u32bit>(key, 1);
state[3] = load_le<u32bit>(key, 2);
state[4] = load_le<u32bit>(key, 3);
state[5] = SIGMA[1];
state[10] = SIGMA[2];
state[11] = load_le<u32bit>(key, 4);
state[12] = load_le<u32bit>(key, 5);
state[13] = load_le<u32bit>(key, 6);
state[14] = load_le<u32bit>(key, 7);
state[15] = SIGMA[3];
}
const byte ZERO[8] = { 0 };
resync(ZERO, sizeof(ZERO));
}
/*************************************************
* Return the name of this type *
*************************************************/
void Salsa20::resync(const byte iv[], u32bit length)
{
if(length != IV_LENGTH)
throw Invalid_IV_Length(name(), length);
state[6] = load_le<u32bit>(iv, 0);
state[7] = load_le<u32bit>(iv, 1);
state[8] = 0;
state[9] = 0;
salsa20(buffer.begin(), state);
position = 0;
}
/*************************************************
* Return the name of this type *
*************************************************/
std::string Salsa20::name() const
{
return "Salsa20";
}
/*************************************************
* Clear memory of sensitive data *
*************************************************/
void Salsa20::clear() throw()
{
state.clear();
buffer.clear();
position = 0;
}
/*************************************************
* Salsa20 Constructor *
*************************************************/
Salsa20::Salsa20() : StreamCipher(16, 32, 16, 8)
{
clear();
}
}
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