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/*
* Copyright 2017-2021 The OpenSSL Project Authors. All Rights Reserved.
* Copyright 2014 Cryptography Research, Inc.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*
* Originally written by Mike Hamburg
*/
#ifndef OSSL_CRYPTO_EC_CURVE448_FIELD_H
# define OSSL_CRYPTO_EC_CURVE448_FIELD_H
# include "internal/constant_time.h"
# include <string.h>
# include <assert.h>
# include "word.h"
# define NLIMBS (64/sizeof(word_t))
# define X_SER_BYTES 56
# define SER_BYTES 56
# if defined(__GNUC__) || defined(__clang__)
# define INLINE_UNUSED __inline__ __attribute__((__unused__,__always_inline__))
# define RESTRICT __restrict__
# define ALIGNED __attribute__((__aligned__(16)))
# else
# define INLINE_UNUSED ossl_inline
# define RESTRICT
# define ALIGNED
# endif
typedef struct gf_s {
word_t limb[NLIMBS];
} ALIGNED gf_s, gf[1];
/* RFC 7748 support */
# define X_PUBLIC_BYTES X_SER_BYTES
# define X_PRIVATE_BYTES X_PUBLIC_BYTES
# define X_PRIVATE_BITS 448
static INLINE_UNUSED void gf_copy(gf out, const gf a)
{
*out = *a;
}
static INLINE_UNUSED void gf_add_RAW(gf out, const gf a, const gf b);
static INLINE_UNUSED void gf_sub_RAW(gf out, const gf a, const gf b);
static INLINE_UNUSED void gf_bias(gf inout, int amount);
static INLINE_UNUSED void gf_weak_reduce(gf inout);
void gf_strong_reduce(gf inout);
void gf_add(gf out, const gf a, const gf b);
void gf_sub(gf out, const gf a, const gf b);
void gf_mul(gf_s * RESTRICT out, const gf a, const gf b);
void gf_mulw_unsigned(gf_s * RESTRICT out, const gf a, uint32_t b);
void gf_sqr(gf_s * RESTRICT out, const gf a);
mask_t gf_isr(gf a, const gf x); /** a^2 x = 1, QNR, or 0 if x=0. Return true if successful */
mask_t gf_eq(const gf x, const gf y);
mask_t gf_lobit(const gf x);
mask_t gf_hibit(const gf x);
void gf_serialize(uint8_t serial[SER_BYTES], const gf x, int with_highbit);
mask_t gf_deserialize(gf x, const uint8_t serial[SER_BYTES], int with_hibit,
uint8_t hi_nmask);
# include "f_impl.h" /* Bring in the inline implementations */
# define LIMBPERM(i) (i)
# define LIMB_MASK(i) (((1)<<LIMB_PLACE_VALUE(i))-1)
static const gf ZERO = {{{0}}}, ONE = {{{1}}};
/* Square x, n times. */
static ossl_inline void gf_sqrn(gf_s * RESTRICT y, const gf x, int n)
{
gf tmp;
assert(n > 0);
if (n & 1) {
gf_sqr(y, x);
n--;
} else {
gf_sqr(tmp, x);
gf_sqr(y, tmp);
n -= 2;
}
for (; n; n -= 2) {
gf_sqr(tmp, y);
gf_sqr(y, tmp);
}
}
# define gf_add_nr gf_add_RAW
/* Subtract mod p. Bias by 2 and don't reduce */
static ossl_inline void gf_sub_nr(gf c, const gf a, const gf b)
{
gf_sub_RAW(c, a, b);
gf_bias(c, 2);
if (GF_HEADROOM < 3)
gf_weak_reduce(c);
}
/* Subtract mod p. Bias by amt but don't reduce. */
static ossl_inline void gf_subx_nr(gf c, const gf a, const gf b, int amt)
{
gf_sub_RAW(c, a, b);
gf_bias(c, amt);
if (GF_HEADROOM < amt + 1)
gf_weak_reduce(c);
}
/* Mul by signed int. Not constant-time WRT the sign of that int. */
static ossl_inline void gf_mulw(gf c, const gf a, int32_t w)
{
if (w > 0) {
gf_mulw_unsigned(c, a, w);
} else {
gf_mulw_unsigned(c, a, -w);
gf_sub(c, ZERO, c);
}
}
/* Constant time, x = is_z ? z : y */
static ossl_inline void gf_cond_sel(gf x, const gf y, const gf z, mask_t is_z)
{
size_t i;
for (i = 0; i < NLIMBS; i++) {
#if ARCH_WORD_BITS == 32
x[0].limb[i] = constant_time_select_32(is_z, z[0].limb[i],
y[0].limb[i]);
#else
/* Must be 64 bit */
x[0].limb[i] = constant_time_select_64(is_z, z[0].limb[i],
y[0].limb[i]);
#endif
}
}
/* Constant time, if (neg) x=-x; */
static ossl_inline void gf_cond_neg(gf x, mask_t neg)
{
gf y;
gf_sub(y, ZERO, x);
gf_cond_sel(x, x, y, neg);
}
/* Constant time, if (swap) (x,y) = (y,x); */
static ossl_inline void gf_cond_swap(gf x, gf_s * RESTRICT y, mask_t swap)
{
size_t i;
for (i = 0; i < NLIMBS; i++) {
#if ARCH_WORD_BITS == 32
constant_time_cond_swap_32(swap, &(x[0].limb[i]), &(y->limb[i]));
#else
/* Must be 64 bit */
constant_time_cond_swap_64(swap, &(x[0].limb[i]), &(y->limb[i]));
#endif
}
}
#endif /* OSSL_CRYPTO_EC_CURVE448_FIELD_H */
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