1 /* 2 * Copyright 2017-2021 The OpenSSL Project Authors. All Rights Reserved. 3 * Copyright 2014 Cryptography Research, Inc. 4 * 5 * Licensed under the OpenSSL license (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 35 typedef 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 44 static INLINE_UNUSED void gf_copy(gf out, const gf a) 45 { 46 *out = *a; 47 } 48 49 static INLINE_UNUSED void gf_add_RAW(gf out, const gf a, const gf b); 50 static INLINE_UNUSED void gf_sub_RAW(gf out, const gf a, const gf b); 51 static INLINE_UNUSED void gf_bias(gf inout, int amount); 52 static INLINE_UNUSED void gf_weak_reduce(gf inout); 53 54 void gf_strong_reduce(gf inout); 55 void gf_add(gf out, const gf a, const gf b); 56 void gf_sub(gf out, const gf a, const gf b); 57 void gf_mul(gf_s * RESTRICT out, const gf a, const gf b); 58 void gf_mulw_unsigned(gf_s * RESTRICT out, const gf a, uint32_t b); 59 void gf_sqr(gf_s * RESTRICT out, const gf a); 60 mask_t gf_isr(gf a, const gf x); /** a^2 x = 1, QNR, or 0 if x=0. Return true if successful */ 61 mask_t gf_eq(const gf x, const gf y); 62 mask_t gf_lobit(const gf x); 63 mask_t gf_hibit(const gf x); 64 65 void gf_serialize(uint8_t serial[SER_BYTES], const gf x, int with_highbit); 66 mask_t gf_deserialize(gf x, const uint8_t serial[SER_BYTES], int with_hibit, 67 uint8_t hi_nmask); 68 69 # include "f_impl.h" /* Bring in the inline implementations */ 70 71 # define LIMBPERM(i) (i) 72 # define LIMB_MASK(i) (((1)<<LIMB_PLACE_VALUE(i))-1) 73 74 static const gf ZERO = {{{0}}}, ONE = {{{1}}}; 75 76 /* Square x, n times. */ 77 static ossl_inline void gf_sqrn(gf_s * RESTRICT y, const gf x, int n) 78 { 79 gf tmp; 80 81 assert(n > 0); 82 if (n & 1) { 83 gf_sqr(y, x); 84 n--; 85 } else { 86 gf_sqr(tmp, x); 87 gf_sqr(y, tmp); 88 n -= 2; 89 } 90 for (; n; n -= 2) { 91 gf_sqr(tmp, y); 92 gf_sqr(y, tmp); 93 } 94 } 95 96 # define gf_add_nr gf_add_RAW 97 98 /* Subtract mod p. Bias by 2 and don't reduce */ 99 static ossl_inline void gf_sub_nr(gf c, const gf a, const gf b) 100 { 101 gf_sub_RAW(c, a, b); 102 gf_bias(c, 2); 103 if (GF_HEADROOM < 3) 104 gf_weak_reduce(c); 105 } 106 107 /* Subtract mod p. Bias by amt but don't reduce. */ 108 static ossl_inline void gf_subx_nr(gf c, const gf a, const gf b, int amt) 109 { 110 gf_sub_RAW(c, a, b); 111 gf_bias(c, amt); 112 if (GF_HEADROOM < amt + 1) 113 gf_weak_reduce(c); 114 } 115 116 /* Mul by signed int. Not constant-time WRT the sign of that int. */ 117 static ossl_inline void gf_mulw(gf c, const gf a, int32_t w) 118 { 119 if (w > 0) { 120 gf_mulw_unsigned(c, a, w); 121 } else { 122 gf_mulw_unsigned(c, a, -w); 123 gf_sub(c, ZERO, c); 124 } 125 } 126 127 /* Constant time, x = is_z ? z : y */ 128 static ossl_inline void gf_cond_sel(gf x, const gf y, const gf z, mask_t is_z) 129 { 130 size_t i; 131 132 for (i = 0; i < NLIMBS; i++) { 133 #if ARCH_WORD_BITS == 32 134 x[0].limb[i] = constant_time_select_32(is_z, z[0].limb[i], 135 y[0].limb[i]); 136 #else 137 /* Must be 64 bit */ 138 x[0].limb[i] = constant_time_select_64(is_z, z[0].limb[i], 139 y[0].limb[i]); 140 #endif 141 } 142 } 143 144 /* Constant time, if (neg) x=-x; */ 145 static ossl_inline void gf_cond_neg(gf x, mask_t neg) 146 { 147 gf y; 148 149 gf_sub(y, ZERO, x); 150 gf_cond_sel(x, x, y, neg); 151 } 152 153 /* Constant time, if (swap) (x,y) = (y,x); */ 154 static ossl_inline void gf_cond_swap(gf x, gf_s * RESTRICT y, mask_t swap) 155 { 156 size_t i; 157 158 for (i = 0; i < NLIMBS; i++) { 159 #if ARCH_WORD_BITS == 32 160 constant_time_cond_swap_32(swap, &(x[0].limb[i]), &(y->limb[i])); 161 #else 162 /* Must be 64 bit */ 163 constant_time_cond_swap_64(swap, &(x[0].limb[i]), &(y->limb[i])); 164 #endif 165 } 166 } 167 168 #endif /* OSSL_CRYPTO_EC_CURVE448_FIELD_H */ 169