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/*
* IDEA
* (C) 1999-2010,2015 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/idea.h>
#include <botan/internal/loadstor.h>
#include <botan/cpuid.h>
#include <botan/internal/ct_utils.h>
namespace Botan {
namespace {
/*
* Multiplication modulo 65537
*/
inline uint16_t mul(uint16_t x, uint16_t y)
{
const uint32_t P = static_cast<uint32_t>(x) * y;
const auto P_mask = CT::Mask<uint16_t>(CT::Mask<uint32_t>::is_zero(P));
const uint32_t P_hi = P >> 16;
const uint32_t P_lo = P & 0xFFFF;
const uint16_t carry = (P_lo < P_hi);
const uint16_t r_1 = static_cast<uint16_t>((P_lo - P_hi) + carry);
const uint16_t r_2 = 1 - x - y;
return P_mask.select(r_2, r_1);
}
/*
* Find multiplicative inverses modulo 65537
*
* 65537 is prime; thus Fermat's little theorem tells us that
* x^65537 == x modulo 65537, which means
* x^(65537-2) == x^-1 modulo 65537 since
* x^(65537-2) * x == 1 mod 65537
*
* Do the exponentiation with a basic square and multiply: all bits are
* of exponent are 1 so we always multiply
*/
uint16_t mul_inv(uint16_t x)
{
uint16_t y = x;
for(size_t i = 0; i != 15; ++i)
{
y = mul(y, y); // square
y = mul(y, x);
}
return y;
}
/**
* IDEA is involutional, depending only on the key schedule
*/
void idea_op(const uint8_t in[], uint8_t out[], size_t blocks, const uint16_t K[52])
{
const size_t BLOCK_SIZE = 8;
CT::poison(in, blocks * 8);
CT::poison(out, blocks * 8);
CT::poison(K, 52);
BOTAN_PARALLEL_FOR(size_t i = 0; i < blocks; ++i)
{
uint16_t X1, X2, X3, X4;
load_be(in + BLOCK_SIZE*i, X1, X2, X3, X4);
for(size_t j = 0; j != 8; ++j)
{
X1 = mul(X1, K[6*j+0]);
X2 += K[6*j+1];
X3 += K[6*j+2];
X4 = mul(X4, K[6*j+3]);
const uint16_t T0 = X3;
X3 = mul(X3 ^ X1, K[6*j+4]);
const uint16_t T1 = X2;
X2 = mul((X2 ^ X4) + X3, K[6*j+5]);
X3 += X2;
X1 ^= X2;
X4 ^= X3;
X2 ^= T0;
X3 ^= T1;
}
X1 = mul(X1, K[48]);
X2 += K[50];
X3 += K[49];
X4 = mul(X4, K[51]);
store_be(out + BLOCK_SIZE*i, X1, X3, X2, X4);
}
CT::unpoison(in, blocks * 8);
CT::unpoison(out, blocks * 8);
CT::unpoison(K, 52);
}
}
size_t IDEA::parallelism() const
{
#if defined(BOTAN_HAS_IDEA_SSE2)
if(CPUID::has_sse2())
{
return 8;
}
#endif
return 1;
}
std::string IDEA::provider() const
{
#if defined(BOTAN_HAS_IDEA_SSE2)
if(CPUID::has_sse2())
{
return "sse2";
}
#endif
return "base";
}
/*
* IDEA Encryption
*/
void IDEA::encrypt_n(const uint8_t in[], uint8_t out[], size_t blocks) const
{
verify_key_set(m_EK.empty() == false);
#if defined(BOTAN_HAS_IDEA_SSE2)
if(CPUID::has_sse2())
{
while(blocks >= 8)
{
sse2_idea_op_8(in, out, m_EK.data());
in += 8 * BLOCK_SIZE;
out += 8 * BLOCK_SIZE;
blocks -= 8;
}
}
#endif
idea_op(in, out, blocks, m_EK.data());
}
/*
* IDEA Decryption
*/
void IDEA::decrypt_n(const uint8_t in[], uint8_t out[], size_t blocks) const
{
verify_key_set(m_DK.empty() == false);
#if defined(BOTAN_HAS_IDEA_SSE2)
if(CPUID::has_sse2())
{
while(blocks >= 8)
{
sse2_idea_op_8(in, out, m_DK.data());
in += 8 * BLOCK_SIZE;
out += 8 * BLOCK_SIZE;
blocks -= 8;
}
}
#endif
idea_op(in, out, blocks, m_DK.data());
}
/*
* IDEA Key Schedule
*/
void IDEA::key_schedule(const uint8_t key[], size_t)
{
m_EK.resize(52);
m_DK.resize(52);
CT::poison(key, 16);
CT::poison(m_EK.data(), 52);
CT::poison(m_DK.data(), 52);
secure_vector<uint64_t> K(2);
K[0] = load_be<uint64_t>(key, 0);
K[1] = load_be<uint64_t>(key, 1);
for(size_t off = 0; off != 48; off += 8)
{
for(size_t i = 0; i != 8; ++i)
m_EK[off+i] = static_cast<uint16_t>(K[i/4] >> (48-16*(i % 4)));
const uint64_t Kx = (K[0] >> 39);
const uint64_t Ky = (K[1] >> 39);
K[0] = (K[0] << 25) | Ky;
K[1] = (K[1] << 25) | Kx;
}
for(size_t i = 0; i != 4; ++i)
m_EK[48+i] = static_cast<uint16_t>(K[i/4] >> (48-16*(i % 4)));
m_DK[0] = mul_inv(m_EK[48]);
m_DK[1] = -m_EK[49];
m_DK[2] = -m_EK[50];
m_DK[3] = mul_inv(m_EK[51]);
for(size_t i = 0; i != 8*6; i += 6)
{
m_DK[i+4] = m_EK[46-i];
m_DK[i+5] = m_EK[47-i];
m_DK[i+6] = mul_inv(m_EK[42-i]);
m_DK[i+7] = -m_EK[44-i];
m_DK[i+8] = -m_EK[43-i];
m_DK[i+9] = mul_inv(m_EK[45-i]);
}
std::swap(m_DK[49], m_DK[50]);
CT::unpoison(key, 16);
CT::unpoison(m_EK.data(), 52);
CT::unpoison(m_DK.data(), 52);
}
void IDEA::clear()
{
zap(m_EK);
zap(m_DK);
}
}
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