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/*
* Salsa20 / XSalsa20
* (C) 1999-2010,2014 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/salsa20.h>
#include <botan/loadstor.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);
}
}
#undef SALSA20_QUARTER_ROUND
/*
* Combine cipher stream with message
*/
void Salsa20::cipher(const byte in[], byte out[], size_t length)
{
while(length >= m_buffer.size() - m_position)
{
xor_buf(out, in, &m_buffer[m_position], m_buffer.size() - m_position);
length -= (m_buffer.size() - m_position);
in += (m_buffer.size() - m_position);
out += (m_buffer.size() - m_position);
salsa20(m_buffer.data(), m_state.data());
++m_state[8];
m_state[9] += (m_state[8] == 0);
m_position = 0;
}
xor_buf(out, in, &m_buffer[m_position], length);
m_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 };
const u32bit* CONSTANTS = (length == 16) ? TAU : SIGMA;
m_state.resize(16);
m_buffer.resize(64);
m_state[0] = CONSTANTS[0];
m_state[5] = CONSTANTS[1];
m_state[10] = CONSTANTS[2];
m_state[15] = CONSTANTS[3];
m_state[1] = load_le<u32bit>(key, 0);
m_state[2] = load_le<u32bit>(key, 1);
m_state[3] = load_le<u32bit>(key, 2);
m_state[4] = load_le<u32bit>(key, 3);
if(length == 32)
key += 16;
m_state[11] = load_le<u32bit>(key, 0);
m_state[12] = load_le<u32bit>(key, 1);
m_state[13] = load_le<u32bit>(key, 2);
m_state[14] = load_le<u32bit>(key, 3);
m_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
m_state[6] = load_le<u32bit>(iv, 0);
m_state[7] = load_le<u32bit>(iv, 1);
}
else
{
// XSalsa20
m_state[6] = load_le<u32bit>(iv, 0);
m_state[7] = load_le<u32bit>(iv, 1);
m_state[8] = load_le<u32bit>(iv, 2);
m_state[9] = load_le<u32bit>(iv, 3);
secure_vector<u32bit> hsalsa(8);
hsalsa20(hsalsa.data(), m_state.data());
m_state[ 1] = hsalsa[0];
m_state[ 2] = hsalsa[1];
m_state[ 3] = hsalsa[2];
m_state[ 4] = hsalsa[3];
m_state[ 6] = load_le<u32bit>(iv, 4);
m_state[ 7] = load_le<u32bit>(iv, 5);
m_state[11] = hsalsa[4];
m_state[12] = hsalsa[5];
m_state[13] = hsalsa[6];
m_state[14] = hsalsa[7];
}
m_state[8] = 0;
m_state[9] = 0;
salsa20(m_buffer.data(), m_state.data());
++m_state[8];
m_state[9] += (m_state[8] == 0);
m_position = 0;
}
/*
* Return the name of this type
*/
std::string Salsa20::name() const
{
return "Salsa20";
}
/*
* Clear memory of sensitive data
*/
void Salsa20::clear()
{
zap(m_state);
zap(m_buffer);
m_position = 0;
}
}
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