1/* 2 * Copyright 2017-2021 The OpenSSL Project Authors. All Rights Reserved. 3 * Copyright 2014 Cryptography Research, Inc. 4 * 5 * Licensed under the Apache License 2.0 (the "License"). You may not use 6 * this file except in compliance with the License. You can obtain a copy 7 * in the file LICENSE in the source distribution or at 8 * https://www.openssl.org/source/license.html 9 * 10 * Originally written by Mike Hamburg 11 */ 12 13#ifndef OSSL_CRYPTO_EC_CURVE448_FIELD_H 14# define OSSL_CRYPTO_EC_CURVE448_FIELD_H 15 16# include "internal/constant_time.h" 17# include <string.h> 18# include <assert.h> 19# include "word.h" 20 21# define NLIMBS (64/sizeof(word_t)) 22# define X_SER_BYTES 56 23# define SER_BYTES 56 24 25# if defined(__GNUC__) || defined(__clang__) 26# define INLINE_UNUSED __inline__ __attribute__((__unused__,__always_inline__)) 27# define RESTRICT __restrict__ 28# define ALIGNED __attribute__((__aligned__(16))) 29# else 30# define INLINE_UNUSED ossl_inline 31# define RESTRICT 32# define ALIGNED 33# endif 34 35typedef struct gf_s { 36 word_t limb[NLIMBS]; 37} ALIGNED gf_s, gf[1]; 38 39/* RFC 7748 support */ 40# define X_PUBLIC_BYTES X_SER_BYTES 41# define X_PRIVATE_BYTES X_PUBLIC_BYTES 42# define X_PRIVATE_BITS 448 43 44static INLINE_UNUSED void gf_copy(gf out, const gf a) 45{ 46 *out = *a; 47} 48 49static INLINE_UNUSED void gf_add_RAW(gf out, const gf a, const gf b); 50static INLINE_UNUSED void gf_sub_RAW(gf out, const gf a, const gf b); 51static INLINE_UNUSED void gf_bias(gf inout, int amount); 52static INLINE_UNUSED void gf_weak_reduce(gf inout); 53 54void gf_strong_reduce(gf inout); 55void gf_add(gf out, const gf a, const gf b); 56void gf_sub(gf out, const gf a, const gf b); 57void gf_mul(gf_s * RESTRICT out, const gf a, const gf b); 58void gf_mulw_unsigned(gf_s * RESTRICT out, const gf a, uint32_t b); 59void gf_sqr(gf_s * RESTRICT out, const gf a); 60mask_t gf_isr(gf a, const gf x); /** a^2 x = 1, QNR, or 0 if x=0. Return true if successful */ 61mask_t gf_eq(const gf x, const gf y); 62mask_t gf_lobit(const gf x); 63mask_t gf_hibit(const gf x); 64 65void gf_serialize(uint8_t *serial, const gf x, int with_highbit); 66mask_t gf_deserialize(gf x, const uint8_t serial[SER_BYTES], int with_hibit, 67 uint8_t hi_nmask); 68 69 70# define LIMBPERM(i) (i) 71# if (ARCH_WORD_BITS == 32) 72# include "arch_32/f_impl.h" /* Bring in the inline implementations */ 73# define LIMB_MASK(i) (((1)<<LIMB_PLACE_VALUE(i))-1) 74# elif (ARCH_WORD_BITS == 64) 75# include "arch_64/f_impl.h" /* Bring in the inline implementations */ 76# define LIMB_MASK(i) (((1ULL)<<LIMB_PLACE_VALUE(i))-1) 77# endif 78 79static const gf ZERO = {{{0}}}, ONE = {{{1}}}; 80 81/* Square x, n times. */ 82static ossl_inline void gf_sqrn(gf_s * RESTRICT y, const gf x, int n) 83{ 84 gf tmp; 85 86 assert(n > 0); 87 if (n & 1) { 88 gf_sqr(y, x); 89 n--; 90 } else { 91 gf_sqr(tmp, x); 92 gf_sqr(y, tmp); 93 n -= 2; 94 } 95 for (; n; n -= 2) { 96 gf_sqr(tmp, y); 97 gf_sqr(y, tmp); 98 } 99} 100 101# define gf_add_nr gf_add_RAW 102 103/* Subtract mod p. Bias by 2 and don't reduce */ 104static ossl_inline void gf_sub_nr(gf c, const gf a, const gf b) 105{ 106 gf_sub_RAW(c, a, b); 107 gf_bias(c, 2); 108 if (GF_HEADROOM < 3) 109 gf_weak_reduce(c); 110} 111 112/* Subtract mod p. Bias by amt but don't reduce. */ 113static ossl_inline void gf_subx_nr(gf c, const gf a, const gf b, int amt) 114{ 115 gf_sub_RAW(c, a, b); 116 gf_bias(c, amt); 117 if (GF_HEADROOM < amt + 1) 118 gf_weak_reduce(c); 119} 120 121/* Mul by signed int. Not constant-time WRT the sign of that int. */ 122static ossl_inline void gf_mulw(gf c, const gf a, int32_t w) 123{ 124 if (w > 0) { 125 gf_mulw_unsigned(c, a, w); 126 } else { 127 gf_mulw_unsigned(c, a, -w); 128 gf_sub(c, ZERO, c); 129 } 130} 131 132/* Constant time, x = is_z ? z : y */ 133static ossl_inline void gf_cond_sel(gf x, const gf y, const gf z, mask_t is_z) 134{ 135 size_t i; 136 137 for (i = 0; i < NLIMBS; i++) { 138#if ARCH_WORD_BITS == 32 139 x[0].limb[i] = constant_time_select_32(is_z, z[0].limb[i], 140 y[0].limb[i]); 141#else 142 /* Must be 64 bit */ 143 x[0].limb[i] = constant_time_select_64(is_z, z[0].limb[i], 144 y[0].limb[i]); 145#endif 146 } 147} 148 149/* Constant time, if (neg) x=-x; */ 150static ossl_inline void gf_cond_neg(gf x, mask_t neg) 151{ 152 gf y; 153 154 gf_sub(y, ZERO, x); 155 gf_cond_sel(x, x, y, neg); 156} 157 158/* Constant time, if (swap) (x,y) = (y,x); */ 159static ossl_inline void gf_cond_swap(gf x, gf_s * RESTRICT y, mask_t swap) 160{ 161 size_t i; 162 163 for (i = 0; i < NLIMBS; i++) { 164#if ARCH_WORD_BITS == 32 165 constant_time_cond_swap_32(swap, &(x[0].limb[i]), &(y->limb[i])); 166#else 167 /* Must be 64 bit */ 168 constant_time_cond_swap_64(swap, &(x[0].limb[i]), &(y->limb[i])); 169#endif 170 } 171} 172 173#endif /* OSSL_CRYPTO_EC_CURVE448_FIELD_H */ 174