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/*
* (C) 2024 Jack Lloyd
*
* Botan is released under the Simplified BSD License (see license.txt)
*/
#include <botan/internal/pcurves_instance.h>
#include <botan/internal/pcurves_solinas.h>
#include <botan/internal/pcurves_wrap.h>
namespace Botan::PCurve {
namespace {
namespace sm2p256v1 {
template <typename Params>
class Sm2p256v1Rep final {
public:
static constexpr auto P = Params::P;
static constexpr size_t N = Params::N;
typedef typename Params::W W;
constexpr static std::array<W, N> redc(const std::array<W, 2 * N>& z) {
const int64_t X00 = get_uint32(z.data(), 0);
const int64_t X01 = get_uint32(z.data(), 1);
const int64_t X02 = get_uint32(z.data(), 2);
const int64_t X03 = get_uint32(z.data(), 3);
const int64_t X04 = get_uint32(z.data(), 4);
const int64_t X05 = get_uint32(z.data(), 5);
const int64_t X06 = get_uint32(z.data(), 6);
const int64_t X07 = get_uint32(z.data(), 7);
const int64_t X08 = get_uint32(z.data(), 8);
const int64_t X09 = get_uint32(z.data(), 9);
const int64_t X10 = get_uint32(z.data(), 10);
const int64_t X11 = get_uint32(z.data(), 11);
const int64_t X12 = get_uint32(z.data(), 12);
const int64_t X13 = get_uint32(z.data(), 13);
const int64_t X14 = get_uint32(z.data(), 14);
const int64_t X15 = get_uint32(z.data(), 15);
const int64_t S0 = X00 + X08 + X09 + X10 + X11 + X12 + 2 * (X13 + X14 + X15);
const int64_t S1 = X01 + X09 + X10 + X11 + X12 + X13 + 2 * (X14 + X15);
const int64_t S2 = X02 - (X08 + X09 + X13 + X14);
const int64_t S3 = X03 + X08 + X11 + X12 + 2 * X13 + X14 + X15;
const int64_t S4 = X04 + X09 + X12 + X13 + 2 * X14 + X15;
const int64_t S5 = X05 + X10 + X13 + X14 + 2 * X15;
const int64_t S6 = X06 + X11 + X14 + X15;
const int64_t S7 = X07 + X08 + X09 + X10 + X11 + 2 * (X12 + X13 + X14 + X15) + X15;
std::array<W, N> r = {};
SolinasAccum sum(r);
sum.accum(S0);
sum.accum(S1);
sum.accum(S2);
sum.accum(S3);
sum.accum(S4);
sum.accum(S5);
sum.accum(S6);
sum.accum(S7);
const auto S = sum.final_carry(0);
bigint_correct_redc<N>(r, P, sm2_mul_mod_256(S));
return r;
}
constexpr static std::array<W, N> one() { return std::array<W, N>{1}; }
constexpr static std::array<W, N> to_rep(const std::array<W, N>& x) { return x; }
constexpr static std::array<W, N> wide_to_rep(const std::array<W, 2 * N>& x) { return redc(x); }
constexpr static std::array<W, N> from_rep(const std::array<W, N>& z) { return z; }
private:
// Return (i*P) % 2**256
//
// Assumes i is small
constexpr static std::array<W, N> sm2_mul_mod_256(W i) {
static_assert(WordInfo<W>::bits == 32 || WordInfo<W>::bits == 64);
// For small i, multiples of P have a simple structure so it's faster to
// compute the value directly vs a (constant time) table lookup
auto r = P;
if constexpr(WordInfo<W>::bits == 32) {
r[7] -= i;
r[3] -= i;
r[2] += i;
r[0] -= i;
} else {
const uint64_t i32 = static_cast<uint64_t>(i) << 32;
r[3] -= i32;
r[1] -= i32;
r[1] += i;
r[0] -= i;
}
return r;
}
};
// clang-format off
class Params final : public EllipticCurveParameters<
"FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFF",
"FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF00000000FFFFFFFFFFFFFFFC",
"28E9FA9E9D9F5E344D5A9E4BCF6509A7F39789F515AB8F92DDBCBD414D940E93",
"FFFFFFFEFFFFFFFFFFFFFFFFFFFFFFFF7203DF6B21C6052B53BBF40939D54123",
"32C4AE2C1F1981195F9904466A39C9948FE30BBFF2660BE1715A4589334C74C7",
"BC3736A2F4F6779C59BDCEE36B692153D0A9877CC62A474002DF32E52139F0A0"> {
};
// clang-format on
class Curve final : public EllipticCurve<Params, Sm2p256v1Rep> {
public:
// Return the square of the inverse of x
static constexpr FieldElement fe_invert2(const FieldElement& x) {
auto z = x.square();
auto t0 = x * z;
z = t0.square();
z *= x;
auto t1 = z;
t1.square_n(3);
t1 *= z;
auto t2 = t1.square();
z = t2 * x;
t2.square_n(5);
t1 *= t2;
t2 = t1;
t2.square_n(12);
t1 *= t2;
t1.square_n(7);
z *= t1;
t2 = z;
t2.square_n(2);
t1 = t2;
t1.square_n(29);
z *= t1;
t1.square_n(2);
t2 *= t1;
t0 *= t2;
t1.square_n(32);
t1 *= t0;
t1.square_n(64);
t0 *= t1;
t0.square_n(94);
z *= t0;
z.square_n(2);
return z;
}
};
} // namespace sm2p256v1
} // namespace
std::shared_ptr<const PrimeOrderCurve> PCurveInstance::sm2p256v1() {
return PrimeOrderCurveImpl<sm2p256v1::Curve>::instance();
}
} // namespace Botan::PCurve