openssl/crypto/ec/curve448/field.h

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/**
* @file field.h
* @brief Generic gf header.
* @copyright
* Copyright (c) 2014 Cryptography Research, Inc. \n
* Released under the MIT License. See LICENSE.txt for license information.
* @author Mike Hamburg
*/
#ifndef __GF_H__
#define __GF_H__
#include "constant_time.h"
#include "f_field.h"
#include <string.h>
/** Square x, n times. */
static DECAF_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 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 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 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 inline void gf_cond_sel(gf x, const gf y, const gf z, mask_t is_z) {
constant_time_select(x,y,z,sizeof(gf),is_z,0);
}
/** Constant time, if (neg) x=-x; */
static 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 inline void
gf_cond_swap(gf x, gf_s *__restrict__ y, mask_t swap) {
constant_time_cond_swap(x,y,sizeof(gf_s),swap);
}
static DECAF_INLINE void gf_mul_qnr(gf_s *__restrict__ out, const gf x) {
#if P_MOD_8 == 5
/* r = QNR * r0^2 */
gf_mul(out,x,SQRT_MINUS_ONE);
#elif P_MOD_8 == 3 || P_MOD_8 == 7
gf_sub(out,ZERO,x);
#else
#error "Only supporting p=3,5,7 mod 8"
#endif
}
static DECAF_INLINE void gf_div_qnr(gf_s *__restrict__ out, const gf x) {
#if P_MOD_8 == 5
/* r = QNR * r0^2 */
gf_mul(out,x,SQRT_MINUS_ONE);
gf_sub(out,ZERO,out);
#elif P_MOD_8 == 3 || P_MOD_8 == 7
gf_sub(out,ZERO,x);
#else
#error "Only supporting p=3,5,7 mod 8"
#endif
}
#if P_MOD_8 == 5
#define gf_mul_i gf_mul_qnr
#define gf_div_i gf_div_qnr
#endif
#endif // __GF_H__