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/*
* (C) 2017,2018 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/poly_dbl.h>
#include <botan/loadstor.h>
#include <botan/exceptn.h>
namespace Botan {
namespace {
/*
* The minimum weight irreducible binary polynomial of size n
*
* See http://www.hpl.hp.com/techreports/98/HPL-98-135.pdf
*/
enum class MinWeightPolynomial : uint64_t {
P64 = 0x1B,
P128 = 0x87,
P192 = 0x87,
P256 = 0x425,
P512 = 0x125,
P1024 = 0x80043,
};
template<size_t LIMBS, MinWeightPolynomial P>
void poly_double(uint8_t out[], const uint8_t in[])
{
uint64_t W[LIMBS];
load_be(W, in, LIMBS);
const uint64_t POLY = static_cast<uint64_t>(P);
const uint64_t carry = POLY * (W[0] >> 63);
BOTAN_IF_CONSTEXPR(LIMBS > 0)
{
for(size_t i = 0; i != LIMBS - 1; ++i)
W[i] = (W[i] << 1) ^ (W[i+1] >> 63);
}
W[LIMBS-1] = (W[LIMBS-1] << 1) ^ carry;
copy_out_be(out, LIMBS*8, W);
}
template<size_t LIMBS, MinWeightPolynomial P>
void poly_double_le(uint8_t out[], const uint8_t in[])
{
uint64_t W[LIMBS];
load_le(W, in, LIMBS);
const uint64_t POLY = static_cast<uint64_t>(P);
const uint64_t carry = POLY * (W[LIMBS-1] >> 63);
BOTAN_IF_CONSTEXPR(LIMBS > 0)
{
for(size_t i = 0; i != LIMBS - 1; ++i)
W[LIMBS-1-i] = (W[LIMBS-1-i] << 1) ^ (W[LIMBS-2-i] >> 63);
}
W[0] = (W[0] << 1) ^ carry;
copy_out_le(out, LIMBS*8, W);
}
}
void poly_double_n(uint8_t out[], const uint8_t in[], size_t n)
{
switch(n)
{
case 8:
return poly_double<1, MinWeightPolynomial::P64>(out, in);
case 16:
return poly_double<2, MinWeightPolynomial::P128>(out, in);
case 24:
return poly_double<3, MinWeightPolynomial::P192>(out, in);
case 32:
return poly_double<4, MinWeightPolynomial::P256>(out, in);
case 64:
return poly_double<8, MinWeightPolynomial::P512>(out, in);
case 128:
return poly_double<16, MinWeightPolynomial::P1024>(out, in);
default:
throw Invalid_Argument("Unsupported size for poly_double_n");
}
}
void poly_double_n_le(uint8_t out[], const uint8_t in[], size_t n)
{
switch(n)
{
case 8:
return poly_double_le<1, MinWeightPolynomial::P64>(out, in);
case 16:
return poly_double_le<2, MinWeightPolynomial::P128>(out, in);
case 24:
return poly_double_le<3, MinWeightPolynomial::P192>(out, in);
case 32:
return poly_double_le<4, MinWeightPolynomial::P256>(out, in);
case 64:
return poly_double_le<8, MinWeightPolynomial::P512>(out, in);
case 128:
return poly_double_le<16, MinWeightPolynomial::P1024>(out, in);
default:
throw Invalid_Argument("Unsupported size for poly_double_n_le");
}
}
}
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