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/*
* Salsa20 / XSalsa20
* (C) 1999-2010 Jack Lloyd
*
* Distributed under the terms of the Botan license
*/
#include <botan/salsa20.h>
#include <botan/loadstor.h>
#include <botan/rotate.h>
#include <botan/internal/xor_buf.h>
namespace Botan {
namespace {
#define SALSA20_QUARTER_ROUND(x1, x2, x3, x4) \
do { \
x2 ^= rotate_left(x1 + x4, 7); \
x3 ^= rotate_left(x2 + x1, 9); \
x4 ^= rotate_left(x3 + x2, 13); \
x1 ^= rotate_left(x4 + x3, 18); \
} while(0)
/*
* Generate HSalsa20 cipher stream (for XSalsa20 IV setup)
*/
void hsalsa20(u32bit output[8], const u32bit input[16])
{
u32bit x00 = input[ 0], x01 = input[ 1], x02 = input[ 2], x03 = input[ 3],
x04 = input[ 4], x05 = input[ 5], x06 = input[ 6], x07 = input[ 7],
x08 = input[ 8], x09 = input[ 9], x10 = input[10], x11 = input[11],
x12 = input[12], x13 = input[13], x14 = input[14], x15 = input[15];
for(size_t i = 0; i != 10; ++i)
{
SALSA20_QUARTER_ROUND(x00, x04, x08, x12);
SALSA20_QUARTER_ROUND(x05, x09, x13, x01);
SALSA20_QUARTER_ROUND(x10, x14, x02, x06);
SALSA20_QUARTER_ROUND(x15, x03, x07, x11);
SALSA20_QUARTER_ROUND(x00, x01, x02, x03);
SALSA20_QUARTER_ROUND(x05, x06, x07, x04);
SALSA20_QUARTER_ROUND(x10, x11, x08, x09);
SALSA20_QUARTER_ROUND(x15, x12, x13, x14);
}
output[0] = x00;
output[1] = x05;
output[2] = x10;
output[3] = x15;
output[4] = x06;
output[5] = x07;
output[6] = x08;
output[7] = x09;
}
/*
* Generate Salsa20 cipher stream
*/
void salsa20(byte output[64], const u32bit input[16])
{
u32bit x00 = input[ 0], x01 = input[ 1], x02 = input[ 2], x03 = input[ 3],
x04 = input[ 4], x05 = input[ 5], x06 = input[ 6], x07 = input[ 7],
x08 = input[ 8], x09 = input[ 9], x10 = input[10], x11 = input[11],
x12 = input[12], x13 = input[13], x14 = input[14], x15 = input[15];
for(size_t i = 0; i != 10; ++i)
{
SALSA20_QUARTER_ROUND(x00, x04, x08, x12);
SALSA20_QUARTER_ROUND(x05, x09, x13, x01);
SALSA20_QUARTER_ROUND(x10, x14, x02, x06);
SALSA20_QUARTER_ROUND(x15, x03, x07, x11);
SALSA20_QUARTER_ROUND(x00, x01, x02, x03);
SALSA20_QUARTER_ROUND(x05, x06, x07, x04);
SALSA20_QUARTER_ROUND(x10, x11, x08, x09);
SALSA20_QUARTER_ROUND(x15, x12, x13, x14);
}
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[], size_t length)
{
while(length >= buffer.size() - position)
{
xor_buf(out, in, &buffer[position], buffer.size() - position);
length -= (buffer.size() - position);
in += (buffer.size() - position);
out += (buffer.size() - position);
salsa20(&buffer[0], &state[0]);
++state[8];
if(!state[8]) // if overflow in state[8]
++state[9]; // carry to state[9]
position = 0;
}
xor_buf(out, in, &buffer[position], length);
position += length;
}
/*
* Salsa20 Key Schedule
*/
void Salsa20::key_schedule(const byte key[], size_t length)
{
static const u32bit TAU[] =
{ 0x61707865, 0x3120646e, 0x79622d36, 0x6b206574 };
static const u32bit SIGMA[] =
{ 0x61707865, 0x3320646e, 0x79622d32, 0x6b206574 };
state.resize(16);
buffer.resize(64);
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];
}
position = 0;
const byte ZERO[8] = { 0 };
set_iv(ZERO, sizeof(ZERO));
}
/*
* Return the name of this type
*/
void Salsa20::set_iv(const byte iv[], size_t length)
{
if(!valid_iv_length(length))
throw Invalid_IV_Length(name(), length);
if(length == 8)
{
// Salsa20
state[6] = load_le<u32bit>(iv, 0);
state[7] = load_le<u32bit>(iv, 1);
}
else
{
// XSalsa20
state[6] = load_le<u32bit>(iv, 0);
state[7] = load_le<u32bit>(iv, 1);
state[8] = load_le<u32bit>(iv, 2);
state[9] = load_le<u32bit>(iv, 3);
secure_vector<u32bit> hsalsa(8);
hsalsa20(&hsalsa[0], &state[0]);
state[ 1] = hsalsa[0];
state[ 2] = hsalsa[1];
state[ 3] = hsalsa[2];
state[ 4] = hsalsa[3];
state[ 6] = load_le<u32bit>(iv, 4);
state[ 7] = load_le<u32bit>(iv, 5);
state[11] = hsalsa[4];
state[12] = hsalsa[5];
state[13] = hsalsa[6];
state[14] = hsalsa[7];
}
state[8] = 0;
state[9] = 0;
salsa20(&buffer[0], &state[0]);
++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()
{
zap(state);
zap(buffer);
position = 0;
}
}
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