poly1305.cpp raw
1 // Copyright (c) 2019-present The Bitcoin Core developers
2 // Distributed under the MIT software license, see the accompanying
3 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5 #include <crypto/common.h>
6 #include <crypto/poly1305.h>
7
8 namespace poly1305_donna {
9
10 // Based on the public domain implementation by Andrew Moon
11 // poly1305-donna-32.h from https://github.com/floodyberry/poly1305-donna
12
13 void poly1305_init(poly1305_context *st, const unsigned char key[32]) noexcept {
14 /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
15 st->r[0] = (ReadLE32(&key[ 0]) ) & 0x3ffffff;
16 st->r[1] = (ReadLE32(&key[ 3]) >> 2) & 0x3ffff03;
17 st->r[2] = (ReadLE32(&key[ 6]) >> 4) & 0x3ffc0ff;
18 st->r[3] = (ReadLE32(&key[ 9]) >> 6) & 0x3f03fff;
19 st->r[4] = (ReadLE32(&key[12]) >> 8) & 0x00fffff;
20
21 /* h = 0 */
22 st->h[0] = 0;
23 st->h[1] = 0;
24 st->h[2] = 0;
25 st->h[3] = 0;
26 st->h[4] = 0;
27
28 /* save pad for later */
29 st->pad[0] = ReadLE32(&key[16]);
30 st->pad[1] = ReadLE32(&key[20]);
31 st->pad[2] = ReadLE32(&key[24]);
32 st->pad[3] = ReadLE32(&key[28]);
33
34 st->leftover = 0;
35 st->final = 0;
36 }
37
38 static void poly1305_blocks(poly1305_context *st, const unsigned char *m, size_t bytes) noexcept {
39 const uint32_t hibit = (st->final) ? 0 : (1UL << 24); /* 1 << 128 */
40 uint32_t r0,r1,r2,r3,r4;
41 uint32_t s1,s2,s3,s4;
42 uint32_t h0,h1,h2,h3,h4;
43 uint64_t d0,d1,d2,d3,d4;
44 uint32_t c;
45
46 r0 = st->r[0];
47 r1 = st->r[1];
48 r2 = st->r[2];
49 r3 = st->r[3];
50 r4 = st->r[4];
51
52 s1 = r1 * 5;
53 s2 = r2 * 5;
54 s3 = r3 * 5;
55 s4 = r4 * 5;
56
57 h0 = st->h[0];
58 h1 = st->h[1];
59 h2 = st->h[2];
60 h3 = st->h[3];
61 h4 = st->h[4];
62
63 while (bytes >= POLY1305_BLOCK_SIZE) {
64 /* h += m[i] */
65 h0 += (ReadLE32(m+ 0) ) & 0x3ffffff;
66 h1 += (ReadLE32(m+ 3) >> 2) & 0x3ffffff;
67 h2 += (ReadLE32(m+ 6) >> 4) & 0x3ffffff;
68 h3 += (ReadLE32(m+ 9) >> 6) & 0x3ffffff;
69 h4 += (ReadLE32(m+12) >> 8) | hibit;
70
71 /* h *= r */
72 d0 = ((uint64_t)h0 * r0) + ((uint64_t)h1 * s4) + ((uint64_t)h2 * s3) + ((uint64_t)h3 * s2) + ((uint64_t)h4 * s1);
73 d1 = ((uint64_t)h0 * r1) + ((uint64_t)h1 * r0) + ((uint64_t)h2 * s4) + ((uint64_t)h3 * s3) + ((uint64_t)h4 * s2);
74 d2 = ((uint64_t)h0 * r2) + ((uint64_t)h1 * r1) + ((uint64_t)h2 * r0) + ((uint64_t)h3 * s4) + ((uint64_t)h4 * s3);
75 d3 = ((uint64_t)h0 * r3) + ((uint64_t)h1 * r2) + ((uint64_t)h2 * r1) + ((uint64_t)h3 * r0) + ((uint64_t)h4 * s4);
76 d4 = ((uint64_t)h0 * r4) + ((uint64_t)h1 * r3) + ((uint64_t)h2 * r2) + ((uint64_t)h3 * r1) + ((uint64_t)h4 * r0);
77
78 /* (partial) h %= p */
79 c = (uint32_t)(d0 >> 26); h0 = (uint32_t)d0 & 0x3ffffff;
80 d1 += c; c = (uint32_t)(d1 >> 26); h1 = (uint32_t)d1 & 0x3ffffff;
81 d2 += c; c = (uint32_t)(d2 >> 26); h2 = (uint32_t)d2 & 0x3ffffff;
82 d3 += c; c = (uint32_t)(d3 >> 26); h3 = (uint32_t)d3 & 0x3ffffff;
83 d4 += c; c = (uint32_t)(d4 >> 26); h4 = (uint32_t)d4 & 0x3ffffff;
84 h0 += c * 5; c = (h0 >> 26); h0 = h0 & 0x3ffffff;
85 h1 += c;
86
87 m += POLY1305_BLOCK_SIZE;
88 bytes -= POLY1305_BLOCK_SIZE;
89 }
90
91 st->h[0] = h0;
92 st->h[1] = h1;
93 st->h[2] = h2;
94 st->h[3] = h3;
95 st->h[4] = h4;
96 }
97
98 void poly1305_finish(poly1305_context *st, unsigned char mac[16]) noexcept {
99 uint32_t h0,h1,h2,h3,h4,c;
100 uint32_t g0,g1,g2,g3,g4;
101 uint64_t f;
102 uint32_t mask;
103
104 /* process the remaining block */
105 if (st->leftover) {
106 size_t i = st->leftover;
107 st->buffer[i++] = 1;
108 for (; i < POLY1305_BLOCK_SIZE; i++) {
109 st->buffer[i] = 0;
110 }
111 st->final = 1;
112 poly1305_blocks(st, st->buffer, POLY1305_BLOCK_SIZE);
113 }
114
115 /* fully carry h */
116 h0 = st->h[0];
117 h1 = st->h[1];
118 h2 = st->h[2];
119 h3 = st->h[3];
120 h4 = st->h[4];
121
122 c = h1 >> 26; h1 = h1 & 0x3ffffff;
123 h2 += c; c = h2 >> 26; h2 = h2 & 0x3ffffff;
124 h3 += c; c = h3 >> 26; h3 = h3 & 0x3ffffff;
125 h4 += c; c = h4 >> 26; h4 = h4 & 0x3ffffff;
126 h0 += c * 5; c = h0 >> 26; h0 = h0 & 0x3ffffff;
127 h1 += c;
128
129 /* compute h + -p */
130 g0 = h0 + 5; c = g0 >> 26; g0 &= 0x3ffffff;
131 g1 = h1 + c; c = g1 >> 26; g1 &= 0x3ffffff;
132 g2 = h2 + c; c = g2 >> 26; g2 &= 0x3ffffff;
133 g3 = h3 + c; c = g3 >> 26; g3 &= 0x3ffffff;
134 g4 = h4 + c - (1UL << 26);
135
136 /* select h if h < p, or h + -p if h >= p */
137 mask = (g4 >> ((sizeof(uint32_t) * 8) - 1)) - 1;
138 g0 &= mask;
139 g1 &= mask;
140 g2 &= mask;
141 g3 &= mask;
142 g4 &= mask;
143 mask = ~mask;
144 h0 = (h0 & mask) | g0;
145 h1 = (h1 & mask) | g1;
146 h2 = (h2 & mask) | g2;
147 h3 = (h3 & mask) | g3;
148 h4 = (h4 & mask) | g4;
149
150 /* h = h % (2^128) */
151 h0 = ((h0 ) | (h1 << 26)) & 0xffffffff;
152 h1 = ((h1 >> 6) | (h2 << 20)) & 0xffffffff;
153 h2 = ((h2 >> 12) | (h3 << 14)) & 0xffffffff;
154 h3 = ((h3 >> 18) | (h4 << 8)) & 0xffffffff;
155
156 /* mac = (h + pad) % (2^128) */
157 f = (uint64_t)h0 + st->pad[0] ; h0 = (uint32_t)f;
158 f = (uint64_t)h1 + st->pad[1] + (f >> 32); h1 = (uint32_t)f;
159 f = (uint64_t)h2 + st->pad[2] + (f >> 32); h2 = (uint32_t)f;
160 f = (uint64_t)h3 + st->pad[3] + (f >> 32); h3 = (uint32_t)f;
161
162 WriteLE32(mac + 0, h0);
163 WriteLE32(mac + 4, h1);
164 WriteLE32(mac + 8, h2);
165 WriteLE32(mac + 12, h3);
166
167 /* zero out the state */
168 st->h[0] = 0;
169 st->h[1] = 0;
170 st->h[2] = 0;
171 st->h[3] = 0;
172 st->h[4] = 0;
173 st->r[0] = 0;
174 st->r[1] = 0;
175 st->r[2] = 0;
176 st->r[3] = 0;
177 st->r[4] = 0;
178 st->pad[0] = 0;
179 st->pad[1] = 0;
180 st->pad[2] = 0;
181 st->pad[3] = 0;
182 }
183
184 void poly1305_update(poly1305_context *st, const unsigned char *m, size_t bytes) noexcept {
185 size_t i;
186
187 /* handle leftover */
188 if (st->leftover) {
189 size_t want = (POLY1305_BLOCK_SIZE - st->leftover);
190 if (want > bytes) {
191 want = bytes;
192 }
193 for (i = 0; i < want; i++) {
194 st->buffer[st->leftover + i] = m[i];
195 }
196 bytes -= want;
197 m += want;
198 st->leftover += want;
199 if (st->leftover < POLY1305_BLOCK_SIZE) return;
200 poly1305_blocks(st, st->buffer, POLY1305_BLOCK_SIZE);
201 st->leftover = 0;
202 }
203
204 /* process full blocks */
205 if (bytes >= POLY1305_BLOCK_SIZE) {
206 size_t want = (bytes & ~(POLY1305_BLOCK_SIZE - 1));
207 poly1305_blocks(st, m, want);
208 m += want;
209 bytes -= want;
210 }
211
212 /* store leftover */
213 if (bytes) {
214 for (i = 0; i < bytes; i++) {
215 st->buffer[st->leftover + i] = m[i];
216 }
217 st->leftover += bytes;
218 }
219 }
220
221 } // namespace poly1305_donna
222