crypto/ec/curve448/field.h

   1 /*
   2  * Copyright 2017-2018 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
  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, 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 */