1 /**********************************************************************
2 * Copyright (c) 2015 Andrew Poelstra *
3 * Distributed under the MIT software license, see the accompanying *
4 * file COPYING or http://www.opensource.org/licenses/mit-license.php.*
5 **********************************************************************/
6
7 #ifndef _SECP256K1_SCALAR_REPR_IMPL_H_
8 #define _SECP256K1_SCALAR_REPR_IMPL_H_
9
10 #include "scalar.h"
11
12 #include <string.h>
13
secp256k1_scalar_is_even(const secp256k1_scalar * a)14 SECP256K1_INLINE static int secp256k1_scalar_is_even(const secp256k1_scalar *a) {
15 return !(*a & 1);
16 }
17
secp256k1_scalar_clear(secp256k1_scalar * r)18 SECP256K1_INLINE static void secp256k1_scalar_clear(secp256k1_scalar *r) { *r = 0; }
secp256k1_scalar_set_int(secp256k1_scalar * r,unsigned int v)19 SECP256K1_INLINE static void secp256k1_scalar_set_int(secp256k1_scalar *r, unsigned int v) { *r = v; }
20
secp256k1_scalar_get_bits(const secp256k1_scalar * a,unsigned int offset,unsigned int count)21 SECP256K1_INLINE static unsigned int secp256k1_scalar_get_bits(const secp256k1_scalar *a, unsigned int offset, unsigned int count) {
22 if (offset < 32)
23 return ((*a >> offset) & ((((uint32_t)1) << count) - 1));
24 else
25 return 0;
26 }
27
secp256k1_scalar_get_bits_var(const secp256k1_scalar * a,unsigned int offset,unsigned int count)28 SECP256K1_INLINE static unsigned int secp256k1_scalar_get_bits_var(const secp256k1_scalar *a, unsigned int offset, unsigned int count) {
29 return secp256k1_scalar_get_bits(a, offset, count);
30 }
31
secp256k1_scalar_check_overflow(const secp256k1_scalar * a)32 SECP256K1_INLINE static int secp256k1_scalar_check_overflow(const secp256k1_scalar *a) { return *a >= EXHAUSTIVE_TEST_ORDER; }
33
secp256k1_scalar_add(secp256k1_scalar * r,const secp256k1_scalar * a,const secp256k1_scalar * b)34 static int secp256k1_scalar_add(secp256k1_scalar *r, const secp256k1_scalar *a, const secp256k1_scalar *b) {
35 *r = (*a + *b) % EXHAUSTIVE_TEST_ORDER;
36 return *r < *b;
37 }
38
secp256k1_scalar_cadd_bit(secp256k1_scalar * r,unsigned int bit,int flag)39 static void secp256k1_scalar_cadd_bit(secp256k1_scalar *r, unsigned int bit, int flag) {
40 if (flag && bit < 32)
41 *r += (1 << bit);
42 #ifdef VERIFY
43 VERIFY_CHECK(secp256k1_scalar_check_overflow(r) == 0);
44 #endif
45 }
46
secp256k1_scalar_set_b32(secp256k1_scalar * r,const unsigned char * b32,int * overflow)47 static void secp256k1_scalar_set_b32(secp256k1_scalar *r, const unsigned char *b32, int *overflow) {
48 const int base = 0x100 % EXHAUSTIVE_TEST_ORDER;
49 int i;
50 *r = 0;
51 for (i = 0; i < 32; i++) {
52 *r = ((*r * base) + b32[i]) % EXHAUSTIVE_TEST_ORDER;
53 }
54 /* just deny overflow, it basically always happens */
55 if (overflow) *overflow = 0;
56 }
57
secp256k1_scalar_get_b32(unsigned char * bin,const secp256k1_scalar * a)58 static void secp256k1_scalar_get_b32(unsigned char *bin, const secp256k1_scalar* a) {
59 memset(bin, 0, 32);
60 bin[28] = *a >> 24; bin[29] = *a >> 16; bin[30] = *a >> 8; bin[31] = *a;
61 }
62
secp256k1_scalar_is_zero(const secp256k1_scalar * a)63 SECP256K1_INLINE static int secp256k1_scalar_is_zero(const secp256k1_scalar *a) {
64 return *a == 0;
65 }
66
secp256k1_scalar_negate(secp256k1_scalar * r,const secp256k1_scalar * a)67 static void secp256k1_scalar_negate(secp256k1_scalar *r, const secp256k1_scalar *a) {
68 if (*a == 0) {
69 *r = 0;
70 } else {
71 *r = EXHAUSTIVE_TEST_ORDER - *a;
72 }
73 }
74
secp256k1_scalar_is_one(const secp256k1_scalar * a)75 SECP256K1_INLINE static int secp256k1_scalar_is_one(const secp256k1_scalar *a) {
76 return *a == 1;
77 }
78
secp256k1_scalar_is_high(const secp256k1_scalar * a)79 static int secp256k1_scalar_is_high(const secp256k1_scalar *a) {
80 return *a > EXHAUSTIVE_TEST_ORDER / 2;
81 }
82
secp256k1_scalar_cond_negate(secp256k1_scalar * r,int flag)83 static int secp256k1_scalar_cond_negate(secp256k1_scalar *r, int flag) {
84 if (flag) secp256k1_scalar_negate(r, r);
85 return flag ? -1 : 1;
86 }
87
secp256k1_scalar_mul(secp256k1_scalar * r,const secp256k1_scalar * a,const secp256k1_scalar * b)88 static void secp256k1_scalar_mul(secp256k1_scalar *r, const secp256k1_scalar *a, const secp256k1_scalar *b) {
89 *r = (*a * *b) % EXHAUSTIVE_TEST_ORDER;
90 }
91
secp256k1_scalar_shr_int(secp256k1_scalar * r,int n)92 static int secp256k1_scalar_shr_int(secp256k1_scalar *r, int n) {
93 int ret;
94 VERIFY_CHECK(n > 0);
95 VERIFY_CHECK(n < 16);
96 ret = *r & ((1 << n) - 1);
97 *r >>= n;
98 return ret;
99 }
100
secp256k1_scalar_sqr(secp256k1_scalar * r,const secp256k1_scalar * a)101 static void secp256k1_scalar_sqr(secp256k1_scalar *r, const secp256k1_scalar *a) {
102 *r = (*a * *a) % EXHAUSTIVE_TEST_ORDER;
103 }
104
secp256k1_scalar_split_128(secp256k1_scalar * r1,secp256k1_scalar * r2,const secp256k1_scalar * a)105 static void secp256k1_scalar_split_128(secp256k1_scalar *r1, secp256k1_scalar *r2, const secp256k1_scalar *a) {
106 *r1 = *a;
107 *r2 = 0;
108 }
109
secp256k1_scalar_eq(const secp256k1_scalar * a,const secp256k1_scalar * b)110 SECP256K1_INLINE static int secp256k1_scalar_eq(const secp256k1_scalar *a, const secp256k1_scalar *b) {
111 return *a == *b;
112 }
113
114 #endif
115