1 /*
2 * Copyright 2017-2023 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
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
gf_copy(gf out,const gf a)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 ossl_gf_mul(gf_s * RESTRICT out, const gf a, const gf b);
58 void ossl_gf_mulw_unsigned(gf_s * RESTRICT out, const gf a, uint32_t b);
59 void ossl_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
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
79 static const gf ZERO = {{{0}}}, ONE = {{{1}}};
80
81 /* Square x, n times. */
gf_sqrn(gf_s * RESTRICT y,const gf x,int n)82 static 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 ossl_gf_sqr(y, x);
89 n--;
90 } else {
91 ossl_gf_sqr(tmp, x);
92 ossl_gf_sqr(y, tmp);
93 n -= 2;
94 }
95 for (; n; n -= 2) {
96 ossl_gf_sqr(tmp, y);
97 ossl_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 */
gf_sub_nr(gf c,const gf a,const gf b)104 static 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. */
gf_subx_nr(gf c,const gf a,const gf b,int amt)113 static 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. */
gf_mulw(gf c,const gf a,int32_t w)122 static ossl_inline void gf_mulw(gf c, const gf a, int32_t w)
123 {
124 if (w > 0) {
125 ossl_gf_mulw_unsigned(c, a, w);
126 } else {
127 ossl_gf_mulw_unsigned(c, a, -w);
128 gf_sub(c, ZERO, c);
129 }
130 }
131
132 /* Constant time, x = is_z ? z : y */
gf_cond_sel(gf x,const gf y,const gf z,mask_t is_z)133 static 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; */
gf_cond_neg(gf x,mask_t neg)150 static 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); */
gf_cond_swap(gf x,gf_s * RESTRICT y,mask_t swap)159 static 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
