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/*
* Salsa20
* (C) 1999-2008 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/salsa20.h>
#include <botan/xor_buf.h>
#include <botan/loadstor.h>
namespace Botan {
namespace {
/*
* Generate Salsa20 cipher stream
*/
void salsa20(byte output[64], const u32bit input[16])
{
u32bit x00 = input[0];
u32bit x01 = input[1];
u32bit x02 = input[2];
u32bit x03 = input[3];
u32bit x04 = input[4];
u32bit x05 = input[5];
u32bit x06 = input[6];
u32bit x07 = input[7];
u32bit x08 = input[8];
u32bit x09 = input[9];
u32bit x10 = input[10];
u32bit x11 = input[11];
u32bit x12 = input[12];
u32bit x13 = input[13];
u32bit x14 = input[14];
u32bit x15 = input[15];
for(u32bit i = 0; i != 10; ++i)
{
x04 ^= rotate_left(x00 + x12, 7);
x08 ^= rotate_left(x04 + x00, 9);
x12 ^= rotate_left(x08 + x04, 13);
x00 ^= rotate_left(x12 + x08, 18);
x09 ^= rotate_left(x05 + x01, 7);
x13 ^= rotate_left(x09 + x05, 9);
x01 ^= rotate_left(x13 + x09, 13);
x05 ^= rotate_left(x01 + x13, 18);
x14 ^= rotate_left(x10 + x06, 7);
x02 ^= rotate_left(x14 + x10, 9);
x06 ^= rotate_left(x02 + x14, 13);
x10 ^= rotate_left(x06 + x02, 18);
x03 ^= rotate_left(x15 + x11, 7);
x07 ^= rotate_left(x03 + x15, 9);
x11 ^= rotate_left(x07 + x03, 13);
x15 ^= rotate_left(x11 + x07, 18);
x01 ^= rotate_left(x00 + x03, 7);
x02 ^= rotate_left(x01 + x00, 9);
x03 ^= rotate_left(x02 + x01, 13);
x00 ^= rotate_left(x03 + x02, 18);
x06 ^= rotate_left(x05 + x04, 7);
x07 ^= rotate_left(x06 + x05, 9);
x04 ^= rotate_left(x07 + x06, 13);
x05 ^= rotate_left(x04 + x07, 18);
x11 ^= rotate_left(x10 + x09, 7);
x08 ^= rotate_left(x11 + x10, 9);
x09 ^= rotate_left(x08 + x11, 13);
x10 ^= rotate_left(x09 + x08, 18);
x12 ^= rotate_left(x15 + x14, 7);
x13 ^= rotate_left(x12 + x15, 9);
x14 ^= rotate_left(x13 + x12, 13);
x15 ^= rotate_left(x14 + x13, 18);
}
store_le(x00 + input[ 0], output + 4 * 0);
store_le(x01 + input[ 1], output + 4 * 1);
store_le(x02 + input[ 2], output + 4 * 2);
store_le(x03 + input[ 3], output + 4 * 3);
store_le(x04 + input[ 4], output + 4 * 4);
store_le(x05 + input[ 5], output + 4 * 5);
store_le(x06 + input[ 6], output + 4 * 6);
store_le(x07 + input[ 7], output + 4 * 7);
store_le(x08 + input[ 8], output + 4 * 8);
store_le(x09 + input[ 9], output + 4 * 9);
store_le(x10 + input[10], output + 4 * 10);
store_le(x11 + input[11], output + 4 * 11);
store_le(x12 + input[12], output + 4 * 12);
store_le(x13 + input[13], output + 4 * 13);
store_le(x14 + input[14], output + 4 * 14);
store_le(x15 + input[15], output + 4 * 15);
}
}
/*
* 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);
++state[8];
if(!state[8]) // if overflow in state[8]
++state[9]; // carry to state[9]
position = 0;
}
xor_buf(out, in, buffer.begin() + position, length);
position += length;
}
/*
* Salsa20 Key Schedule
*/
void Salsa20::key_schedule(const byte key[], u32bit length)
{
static const u32bit TAU[] =
{ 0x61707865, 0x3120646e, 0x79622d36, 0x6b206574 };
static const u32bit SIGMA[] =
{ 0x61707865, 0x3320646e, 0x79622d32, 0x6b206574 };
clear();
if(length == 16)
{
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)
{
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 };
set_iv(ZERO, sizeof(ZERO));
}
/*
* Return the name of this type
*/
void Salsa20::set_iv(const byte iv[], u32bit length)
{
if(!valid_iv_length(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);
++state[8];
if(!state[8]) // if overflow in state[8]
++state[9]; // carry to state[9]
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)
{
clear();
}
}
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