1 /******************************************************************************
2 * Filename: sw_poly1305-donna-32.h
3 ******************************************************************************/
4 /*
5 poly1305 implementation using 32 bit * 32 bit = 64 bit multiplication and 64 bit addition
6 */
7
8 #if defined(_MSC_VER)
9 #define POLY1305_NOINLINE __declspec(noinline)
10 #elif defined(__GNUC__)
11 #define POLY1305_NOINLINE __attribute__((noinline))
12 #else
13 #define POLY1305_NOINLINE
14 #endif
15
16 #define poly1305_block_size 16
17
18 /* 17 + sizeof(size_t) + 14*sizeof(unsigned long) */
19 typedef struct {
20 unsigned long r[5];
21 unsigned long h[5];
22 unsigned long pad[4];
23 size_t leftover;
24 unsigned char buffer[poly1305_block_size];
25 unsigned char final;
26 } poly1305_state_internal_t;
27
28 /* interpret four 8 bit unsigned integers as a 32 bit unsigned integer in little endian */
29 static unsigned long
U8TO32(const unsigned char * p)30 U8TO32(const unsigned char *p) {
31 return
32 (((unsigned long)(p[0] & 0xff) ) |
33 ((unsigned long)(p[1] & 0xff) << 8) |
34 ((unsigned long)(p[2] & 0xff) << 16) |
35 ((unsigned long)(p[3] & 0xff) << 24));
36 }
37
38 /* store a 32 bit unsigned integer as four 8 bit unsigned integers in little endian */
39 static void
U32TO8(unsigned char * p,unsigned long v)40 U32TO8(unsigned char *p, unsigned long v) {
41 p[0] = (v ) & 0xff;
42 p[1] = (v >> 8) & 0xff;
43 p[2] = (v >> 16) & 0xff;
44 p[3] = (v >> 24) & 0xff;
45 }
46
47 void
poly1305_init(poly1305_context * ctx,const unsigned char key[32])48 poly1305_init(poly1305_context *ctx, const unsigned char key[32]) {
49 poly1305_state_internal_t *st = (poly1305_state_internal_t *)ctx;
50
51 /* r &= 0xffffffc0ffffffc0ffffffc0fffffff */
52 st->r[0] = (U8TO32(&key[ 0]) ) & 0x3ffffff;
53 st->r[1] = (U8TO32(&key[ 3]) >> 2) & 0x3ffff03;
54 st->r[2] = (U8TO32(&key[ 6]) >> 4) & 0x3ffc0ff;
55 st->r[3] = (U8TO32(&key[ 9]) >> 6) & 0x3f03fff;
56 st->r[4] = (U8TO32(&key[12]) >> 8) & 0x00fffff;
57
58 /* h = 0 */
59 st->h[0] = 0;
60 st->h[1] = 0;
61 st->h[2] = 0;
62 st->h[3] = 0;
63 st->h[4] = 0;
64
65 /* save pad for later */
66 st->pad[0] = U8TO32(&key[16]);
67 st->pad[1] = U8TO32(&key[20]);
68 st->pad[2] = U8TO32(&key[24]);
69 st->pad[3] = U8TO32(&key[28]);
70
71 st->leftover = 0;
72 st->final = 0;
73 }
74
75 static void
poly1305_blocks(poly1305_state_internal_t * st,const unsigned char * m,size_t bytes)76 poly1305_blocks(poly1305_state_internal_t *st, const unsigned char *m, size_t bytes) {
77 const unsigned long hibit = (st->final) ? 0 : (1UL << 24); /* 1 << 128 */
78 unsigned long r0,r1,r2,r3,r4;
79 unsigned long s1,s2,s3,s4;
80 unsigned long h0,h1,h2,h3,h4;
81 unsigned long long d0,d1,d2,d3,d4;
82 unsigned long c;
83
84 r0 = st->r[0];
85 r1 = st->r[1];
86 r2 = st->r[2];
87 r3 = st->r[3];
88 r4 = st->r[4];
89
90 s1 = r1 * 5;
91 s2 = r2 * 5;
92 s3 = r3 * 5;
93 s4 = r4 * 5;
94
95 h0 = st->h[0];
96 h1 = st->h[1];
97 h2 = st->h[2];
98 h3 = st->h[3];
99 h4 = st->h[4];
100
101 while (bytes >= poly1305_block_size) {
102 /* h += m[i] */
103 h0 += (U8TO32(m+ 0) ) & 0x3ffffff;
104 h1 += (U8TO32(m+ 3) >> 2) & 0x3ffffff;
105 h2 += (U8TO32(m+ 6) >> 4) & 0x3ffffff;
106 h3 += (U8TO32(m+ 9) >> 6) & 0x3ffffff;
107 h4 += (U8TO32(m+12) >> 8) | hibit;
108
109 /* h *= r */
110 d0 = ((unsigned long long)h0 * r0) + ((unsigned long long)h1 * s4) + ((unsigned long long)h2 * s3) + ((unsigned long long)h3 * s2) + ((unsigned long long)h4 * s1);
111 d1 = ((unsigned long long)h0 * r1) + ((unsigned long long)h1 * r0) + ((unsigned long long)h2 * s4) + ((unsigned long long)h3 * s3) + ((unsigned long long)h4 * s2);
112 d2 = ((unsigned long long)h0 * r2) + ((unsigned long long)h1 * r1) + ((unsigned long long)h2 * r0) + ((unsigned long long)h3 * s4) + ((unsigned long long)h4 * s3);
113 d3 = ((unsigned long long)h0 * r3) + ((unsigned long long)h1 * r2) + ((unsigned long long)h2 * r1) + ((unsigned long long)h3 * r0) + ((unsigned long long)h4 * s4);
114 d4 = ((unsigned long long)h0 * r4) + ((unsigned long long)h1 * r3) + ((unsigned long long)h2 * r2) + ((unsigned long long)h3 * r1) + ((unsigned long long)h4 * r0);
115
116 /* (partial) h %= p */
117 c = (unsigned long)(d0 >> 26); h0 = (unsigned long)d0 & 0x3ffffff;
118 d1 += c; c = (unsigned long)(d1 >> 26); h1 = (unsigned long)d1 & 0x3ffffff;
119 d2 += c; c = (unsigned long)(d2 >> 26); h2 = (unsigned long)d2 & 0x3ffffff;
120 d3 += c; c = (unsigned long)(d3 >> 26); h3 = (unsigned long)d3 & 0x3ffffff;
121 d4 += c; c = (unsigned long)(d4 >> 26); h4 = (unsigned long)d4 & 0x3ffffff;
122 h0 += c * 5; c = (h0 >> 26); h0 = h0 & 0x3ffffff;
123 h1 += c;
124
125 m += poly1305_block_size;
126 bytes -= poly1305_block_size;
127 }
128
129 st->h[0] = h0;
130 st->h[1] = h1;
131 st->h[2] = h2;
132 st->h[3] = h3;
133 st->h[4] = h4;
134 }
135
136 POLY1305_NOINLINE void
poly1305_finish(poly1305_context * ctx,unsigned char mac[16])137 poly1305_finish(poly1305_context *ctx, unsigned char mac[16]) {
138 poly1305_state_internal_t *st = (poly1305_state_internal_t *)ctx;
139 unsigned long h0,h1,h2,h3,h4,c;
140 unsigned long g0,g1,g2,g3,g4;
141 unsigned long long f;
142 unsigned long mask;
143
144 /* process the remaining block */
145 if (st->leftover) {
146 size_t i = st->leftover;
147 st->buffer[i++] = 1;
148 for (; i < poly1305_block_size; i++)
149 st->buffer[i] = 0;
150 st->final = 1;
151 poly1305_blocks(st, st->buffer, poly1305_block_size);
152 }
153
154 /* fully carry h */
155 h0 = st->h[0];
156 h1 = st->h[1];
157 h2 = st->h[2];
158 h3 = st->h[3];
159 h4 = st->h[4];
160
161 c = h1 >> 26; h1 = h1 & 0x3ffffff;
162 h2 += c; c = h2 >> 26; h2 = h2 & 0x3ffffff;
163 h3 += c; c = h3 >> 26; h3 = h3 & 0x3ffffff;
164 h4 += c; c = h4 >> 26; h4 = h4 & 0x3ffffff;
165 h0 += c * 5; c = h0 >> 26; h0 = h0 & 0x3ffffff;
166 h1 += c;
167
168 /* compute h + -p */
169 g0 = h0 + 5; c = g0 >> 26; g0 &= 0x3ffffff;
170 g1 = h1 + c; c = g1 >> 26; g1 &= 0x3ffffff;
171 g2 = h2 + c; c = g2 >> 26; g2 &= 0x3ffffff;
172 g3 = h3 + c; c = g3 >> 26; g3 &= 0x3ffffff;
173 g4 = h4 + c - (1UL << 26);
174
175 /* select h if h < p, or h + -p if h >= p */
176 mask = (g4 >> ((sizeof(unsigned long) * 8) - 1)) - 1;
177 g0 &= mask;
178 g1 &= mask;
179 g2 &= mask;
180 g3 &= mask;
181 g4 &= mask;
182 mask = ~mask;
183 h0 = (h0 & mask) | g0;
184 h1 = (h1 & mask) | g1;
185 h2 = (h2 & mask) | g2;
186 h3 = (h3 & mask) | g3;
187 h4 = (h4 & mask) | g4;
188
189 /* h = h % (2^128) */
190 h0 = ((h0 ) | (h1 << 26)) & 0xffffffff;
191 h1 = ((h1 >> 6) | (h2 << 20)) & 0xffffffff;
192 h2 = ((h2 >> 12) | (h3 << 14)) & 0xffffffff;
193 h3 = ((h3 >> 18) | (h4 << 8)) & 0xffffffff;
194
195 /* mac = (h + pad) % (2^128) */
196 f = (unsigned long long)h0 + st->pad[0] ; h0 = (unsigned long)f;
197 f = (unsigned long long)h1 + st->pad[1] + (f >> 32); h1 = (unsigned long)f;
198 f = (unsigned long long)h2 + st->pad[2] + (f >> 32); h2 = (unsigned long)f;
199 f = (unsigned long long)h3 + st->pad[3] + (f >> 32); h3 = (unsigned long)f;
200
201 U32TO8(mac + 0, h0);
202 U32TO8(mac + 4, h1);
203 U32TO8(mac + 8, h2);
204 U32TO8(mac + 12, h3);
205
206 /* zero out the state */
207 st->h[0] = 0;
208 st->h[1] = 0;
209 st->h[2] = 0;
210 st->h[3] = 0;
211 st->h[4] = 0;
212 st->r[0] = 0;
213 st->r[1] = 0;
214 st->r[2] = 0;
215 st->r[3] = 0;
216 st->r[4] = 0;
217 st->pad[0] = 0;
218 st->pad[1] = 0;
219 st->pad[2] = 0;
220 st->pad[3] = 0;
221 }
222
