Botan 2.19.2
Crypto and TLS for C&
sc_reduce.cpp
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1/*
2* Ed25519
3* (C) 2017 Ribose Inc
4*
5* Based on the public domain code from SUPERCOP ref10 by
6* Peter Schwabe, Daniel J. Bernstein, Niels Duif, Tanja Lange, Bo-Yin Yang
7*
8* Botan is released under the Simplified BSD License (see license.txt)
9*/
10
11#include <botan/internal/ed25519_internal.h>
12
13namespace Botan {
14
15/*
16Input:
17 s[0]+256*s[1]+...+256^63*s[63] = s
18
19Output:
20 s[0]+256*s[1]+...+256^31*s[31] = s mod l
21 where l = 2^252 + 27742317777372353535851937790883648493.
22 Overwrites s in place.
23*/
24
25void sc_reduce(uint8_t* s)
26 {
27 const uint32_t MASK = 0x1fffff;
28
29 int64_t s0 = MASK & load_3(s);
30 int64_t s1 = MASK & (load_4(s + 2) >> 5);
31 int64_t s2 = MASK & (load_3(s + 5) >> 2);
32 int64_t s3 = MASK & (load_4(s + 7) >> 7);
33 int64_t s4 = MASK & (load_4(s + 10) >> 4);
34 int64_t s5 = MASK & (load_3(s + 13) >> 1);
35 int64_t s6 = MASK & (load_4(s + 15) >> 6);
36 int64_t s7 = MASK & (load_3(s + 18) >> 3);
37 int64_t s8 = MASK & load_3(s + 21);
38 int64_t s9 = MASK & (load_4(s + 23) >> 5);
39 int64_t s10 = MASK & (load_3(s + 26) >> 2);
40 int64_t s11 = MASK & (load_4(s + 28) >> 7);
41 int64_t s12 = MASK & (load_4(s + 31) >> 4);
42 int64_t s13 = MASK & (load_3(s + 34) >> 1);
43 int64_t s14 = MASK & (load_4(s + 36) >> 6);
44 int64_t s15 = MASK & (load_3(s + 39) >> 3);
45 int64_t s16 = MASK & load_3(s + 42);
46 int64_t s17 = MASK & (load_4(s + 44) >> 5);
47 int64_t s18 = MASK & (load_3(s + 47) >> 2);
48 int64_t s19 = MASK & (load_4(s + 49) >> 7);
49 int64_t s20 = MASK & (load_4(s + 52) >> 4);
50 int64_t s21 = MASK & (load_3(s + 55) >> 1);
51 int64_t s22 = MASK & (load_4(s + 57) >> 6);
52 int64_t s23 = (load_4(s + 60) >> 3);
53
54 redc_mul(s11, s12, s13, s14, s15, s16, s23);
55 redc_mul(s10, s11, s12, s13, s14, s15, s22);
56 redc_mul( s9, s10, s11, s12, s13, s14, s21);
57 redc_mul( s8, s9, s10, s11, s12, s13, s20);
58 redc_mul( s7, s8, s9, s10, s11, s12, s19);
59 redc_mul( s6, s7, s8, s9, s10, s11, s18);
60
61 carry<21>(s6, s7);
62 carry<21>(s8, s9);
63 carry<21>(s10, s11);
64 carry<21>(s12, s13);
65 carry<21>(s14, s15);
66 carry<21>(s16, s17);
67
68 carry<21>(s7, s8);
69 carry<21>(s9, s10);
70 carry<21>(s11, s12);
71 carry<21>(s13, s14);
72 carry<21>(s15, s16);
73
74 redc_mul(s5, s6, s7, s8, s9, s10, s17);
75 redc_mul(s4, s5, s6, s7, s8, s9, s16);
76 redc_mul(s3, s4, s5, s6, s7, s8, s15);
77 redc_mul(s2, s3, s4, s5, s6, s7, s14);
78 redc_mul(s1, s2, s3, s4, s5, s6, s13);
79 redc_mul(s0, s1, s2, s3, s4, s5, s12);
80
81 carry<21>(s0, s1);
82 carry<21>(s2, s3);
83 carry<21>(s4, s5);
84 carry<21>(s6, s7);
85 carry<21>(s8, s9);
86 carry<21>(s10, s11);
87
88 carry<21>(s1, s2);
89 carry<21>(s3, s4);
90 carry<21>(s5, s6);
91 carry<21>(s7, s8);
92 carry<21>(s9, s10);
93 carry<21>(s11, s12);
94
95 redc_mul(s0, s1, s2, s3, s4, s5, s12);
96
97 carry0<21>(s0, s1);
98 carry0<21>(s1, s2);
99 carry0<21>(s2, s3);
100 carry0<21>(s3, s4);
101 carry0<21>(s4, s5);
102 carry0<21>(s5, s6);
103 carry0<21>(s6, s7);
104 carry0<21>(s7, s8);
105 carry0<21>(s8, s9);
106 carry0<21>(s9, s10);
107 carry0<21>(s10, s11);
108 carry0<21>(s11, s12);
109
110 redc_mul(s0, s1, s2, s3, s4, s5, s12);
111
112 carry0<21>(s0, s1);
113 carry0<21>(s1, s2);
114 carry0<21>(s2, s3);
115 carry0<21>(s3, s4);
116 carry0<21>(s4, s5);
117 carry0<21>(s5, s6);
118 carry0<21>(s6, s7);
119 carry0<21>(s7, s8);
120 carry0<21>(s8, s9);
121 carry0<21>(s9, s10);
122 carry0<21>(s10, s11);
123 carry0<21>(s11, s12);
124
125 s[0] = static_cast<uint8_t>(s0 >> 0);
126 s[1] = static_cast<uint8_t>(s0 >> 8);
127 s[2] = static_cast<uint8_t>((s0 >> 16) | (s1 << 5));
128 s[3] = static_cast<uint8_t>(s1 >> 3);
129 s[4] = static_cast<uint8_t>(s1 >> 11);
130 s[5] = static_cast<uint8_t>((s1 >> 19) | (s2 << 2));
131 s[6] = static_cast<uint8_t>(s2 >> 6);
132 s[7] = static_cast<uint8_t>((s2 >> 14) | (s3 << 7));
133 s[8] = static_cast<uint8_t>(s3 >> 1);
134 s[9] = static_cast<uint8_t>(s3 >> 9);
135 s[10] = static_cast<uint8_t>((s3 >> 17) | (s4 << 4));
136 s[11] = static_cast<uint8_t>(s4 >> 4);
137 s[12] = static_cast<uint8_t>(s4 >> 12);
138 s[13] = static_cast<uint8_t>((s4 >> 20) | (s5 << 1));
139 s[14] = static_cast<uint8_t>(s5 >> 7);
140 s[15] = static_cast<uint8_t>((s5 >> 15) | (s6 << 6));
141 s[16] = static_cast<uint8_t>(s6 >> 2);
142 s[17] = static_cast<uint8_t>(s6 >> 10);
143 s[18] = static_cast<uint8_t>((s6 >> 18) | (s7 << 3));
144 s[19] = static_cast<uint8_t>(s7 >> 5);
145 s[20] = static_cast<uint8_t>(s7 >> 13);
146 s[21] = static_cast<uint8_t>(s8 >> 0);
147 s[22] = static_cast<uint8_t>(s8 >> 8);
148 s[23] = static_cast<uint8_t>((s8 >> 16) | (s9 << 5));
149 s[24] = static_cast<uint8_t>(s9 >> 3);
150 s[25] = static_cast<uint8_t>(s9 >> 11);
151 s[26] = static_cast<uint8_t>((s9 >> 19) | (s10 << 2));
152 s[27] = static_cast<uint8_t>(s10 >> 6);
153 s[28] = static_cast<uint8_t>((s10 >> 14) | (s11 << 7));
154 s[29] = static_cast<uint8_t>(s11 >> 1);
155 s[30] = static_cast<uint8_t>(s11 >> 9);
156 s[31] = static_cast<uint8_t>(s11 >> 17);
157 }
158
159}
Definition: alg_id.cpp:13
void redc_mul(int64_t &s1, int64_t &s2, int64_t &s3, int64_t &s4, int64_t &s5, int64_t &s6, int64_t &X)
uint64_t load_4(const uint8_t *in)
void sc_reduce(uint8_t *)
Definition: sc_reduce.cpp:25
uint64_t load_3(const uint8_t in[3])