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194e93f2 MW |
1 | /* -*-c-*- |
2 | * | |
3 | * Salsa20 core definitions | |
4 | * | |
5 | * (c) 2015 Straylight/Edgeware | |
6 | */ | |
7 | ||
8 | #ifndef CATACOMB_SALSA20_CORE_H | |
9 | #define CATACOMB_SALSA20_CORE_H | |
10 | ||
11 | #ifdef __cplusplus | |
12 | extern "C" { | |
13 | #endif | |
14 | ||
15 | /*----- Header files ------------------------------------------------------*/ | |
16 | ||
17 | #include <mLib/bits.h> | |
18 | #include <mLib/macros.h> | |
19 | ||
20 | #ifndef CATACOMB_SALSA20_H | |
21 | # include "salsa20.h" | |
22 | #endif | |
23 | ||
24 | /*----- Magic constants ---------------------------------------------------*/ | |
25 | ||
26 | /* The magic Salsa20 constants, for 256-bit keys... */ | |
27 | #define SALSA20_A256 0x61707865 /* e x p a */ | |
28 | #define SALSA20_B256 0x3320646e /* n d 3 */ | |
29 | #define SALSA20_C256 0x79622d32 /* 2 - b y */ | |
30 | #define SALSA20_D256 0x6b206574 /* t e k */ | |
31 | ||
32 | /* ... and for 128-bit keys ... */ | |
33 | #define SALSA20_A128 SALSA20_A256 /* e x p a */ | |
34 | #define SALSA20_B128 0x3120646e /* n d 1 */ | |
35 | #define SALSA20_C128 0x79622d36 /* 6 - b y */ | |
36 | #define SALSA20_D128 SALSA20_D256 /* t e k */ | |
37 | ||
38 | /* ... and for 80-bit keys, for completeness's sake. */ | |
39 | #define SALSA20_A80 SALSA20_A128 /* e x p a */ | |
40 | #define SALSA20_B80 SALSA20_B128 /* n d 1 */ | |
41 | #define SALSA20_C80 0x79622d30 /* 0 - b y */ | |
42 | #define SALSA20_D80 SALSA20_D128 /* t e k */ | |
43 | ||
44 | /*----- The Salsa20 core function -----------------------------------------*/ | |
45 | ||
a4c2e267 MW |
46 | /* It makes life somewhat easier if we don't actually store and maintain the |
47 | * input matrix in the textbook order. Instead, we rotate the columns other | |
48 | * than the leftmost one upwards, so that the constants which were originally | |
49 | * along the diagonal end up on the top row. We'll need to undo this | |
50 | * permutation on output, but that's not too terrible an imposition. | |
51 | * | |
52 | * The permutation we're applying to the matrix elements is this: | |
53 | * | |
54 | * [ 0 1 2 3 ] [ 0 5 10 15 ] | |
55 | * [ 4 5 6 7 ] --> [ 4 9 14 3 ] | |
56 | * [ 8 9 10 11 ] [ 8 13 2 7 ] | |
57 | * [ 12 13 14 15 ] [ 12 1 6 11 ] | |
58 | * | |
59 | * and as a result, we need to apply this inverse permutation to figure out | |
60 | * which indices to use in the doublerow function and elsewhere. | |
61 | * | |
62 | * [ 0 13 10 7 ] | |
63 | * [ 4 1 14 11 ] | |
64 | * [ 8 5 2 15 ] | |
65 | * [ 12 9 6 3 ] | |
66 | */ | |
67 | ||
194e93f2 MW |
68 | /* The Salsa20 quarter-round. Read from the matrix @y@ at indices @a@, @b@, |
69 | * @c@, and @d@; and write to the corresponding elements of @z@. | |
70 | */ | |
71 | #define SALSA20_QR(z, y, a, b, c, d) do { \ | |
72 | (z)[b] = (y)[b] ^ ROL32((y)[a] + (y)[d], 7); \ | |
73 | (z)[c] = (y)[c] ^ ROL32((z)[b] + (y)[a], 9); \ | |
74 | (z)[d] = (y)[d] ^ ROL32((z)[c] + (z)[b], 13); \ | |
75 | (z)[a] = (y)[a] ^ ROL32((z)[d] + (z)[c], 18); \ | |
76 | } while (0) | |
77 | ||
78 | /* The Salsa20 double-round. Read from matrix @y@, writing the result to | |
79 | * @z@. | |
80 | */ | |
81 | #define SALSA20_DR(z, y) do { \ | |
82 | SALSA20_QR(z, y, 0, 4, 8, 12); \ | |
a4c2e267 MW |
83 | SALSA20_QR(z, y, 1, 5, 9, 13); \ |
84 | SALSA20_QR(z, y, 2, 6, 10, 14); \ | |
85 | SALSA20_QR(z, y, 3, 7, 11, 15); \ | |
86 | SALSA20_QR(z, z, 0, 13, 10, 7); \ | |
87 | SALSA20_QR(z, z, 1, 14, 11, 4); \ | |
88 | SALSA20_QR(z, z, 2, 15, 8, 5); \ | |
89 | SALSA20_QR(z, z, 3, 12, 9, 6); \ | |
194e93f2 MW |
90 | } while (0) |
91 | ||
92 | /* The Salsa20 feedforward step, used at the end of the core function. Here, | |
93 | * @y@ contains the original input matrix; @z@ contains the final one, and is | |
a4c2e267 | 94 | * updated. The output is rendered in canonical order, ready for output. |
194e93f2 MW |
95 | */ |
96 | #define SALSA20_FFWD(z, y) do { \ | |
a4c2e267 MW |
97 | const uint32 *_y = (y); \ |
98 | uint32 *_z = (z); \ | |
99 | int _t; \ | |
100 | _z[ 0] = _z[ 0] + _y[ 0]; _z[ 4] = _z[ 4] + _y[ 4]; \ | |
101 | _z[ 8] = _z[ 8] + _y[ 8]; _z[12] = _z[12] + _y[12]; \ | |
102 | _t = _z[ 1] + _y[ 1]; _z[ 1] = _z[13] + _y[13]; \ | |
103 | _z[13] = _z[ 9] + _y[ 9]; _z[ 9] = _z[ 5] + _y[ 5]; _z[ 5] = _t; \ | |
104 | _t = _z[ 2] + _y[ 2]; _z[ 2] = _z[10] + _y[10]; _z[10] = _t; \ | |
105 | _t = _z[ 6] + _y[ 6]; _z[ 6] = _z[14] + _y[14]; _z[14] = _t; \ | |
106 | _t = _z[ 3] + _y[ 3]; _z[ 3] = _z[ 7] + _y[ 7]; \ | |
107 | _z[ 7] = _z[11] + _y[11]; _z[11] = _z[15] + _y[15]; _z[15] = _t; \ | |
194e93f2 MW |
108 | } while (0) |
109 | ||
110 | /* Various numbers of rounds, unrolled. Read from @y@, and write to @z@. */ | |
111 | #define SALSA20_4R(z, y) \ | |
112 | do { SALSA20_DR(z, y); SALSA20_DR(z, z); } while (0) | |
113 | #define SALSA20_8R(z, y) \ | |
114 | do { SALSA20_4R(z, y); SALSA20_4R(z, z); } while (0) | |
115 | #define SALSA20_12R(z, y) \ | |
116 | do { SALSA20_8R(z, y); SALSA20_4R(z, z); } while (0) | |
117 | #define SALSA20_20R(z, y) \ | |
118 | do { SALSA20_12R(z, y); SALSA20_8R(z, z); } while (0) | |
119 | ||
120 | /* Apply @n@ (must be even) rounds, rolled. (This seems to be faster, | |
121 | * probably because it fits in cache better). Read from @y@, and write to | |
122 | * @z@. | |
123 | */ | |
124 | #define SALSA20_nR(z, y, n) do { \ | |
125 | int _i; \ | |
126 | SALSA20_DR(z, y); \ | |
127 | for (_i = 0; _i < (n)/2 - 1; _i++) SALSA20_DR(z, z); \ | |
128 | } while (0) | |
129 | ||
130 | /* Step the counter in the Salsa20 state matrix @a@. */ | |
131 | #define SALSA20_STEP(a) \ | |
a4c2e267 | 132 | do { (a)[8] = U32((a)[8] + 1); (a)[5] += !(a)[8]; } while (0) |
194e93f2 MW |
133 | |
134 | /*----- Buffering and output ----------------------------------------------* | |
135 | * | |
136 | * These macros are also used by ChaCha. | |
137 | */ | |
138 | ||
139 | /* Copy the Salsa20 matrix @a@ to the output buffer at @d@, advancing @d@ | |
140 | * past the new material. | |
141 | */ | |
142 | #define SALSA20_GENFULL(a, d) do { \ | |
143 | int _i; \ | |
144 | \ | |
145 | for (_i = 0; _i < 16; _i++) { STORE32_L((d), (a)[_i]); (d) += 4; } \ | |
146 | } while (0) | |
147 | ||
148 | /* XOR the contents the input buffer at @s@ with the Salsa20 matrix @a@, | |
149 | * writing the result to @d@ and advance @s@ and @d@. | |
150 | */ | |
151 | #define SALSA20_MIXFULL(a, d, s) do { \ | |
152 | uint32 _x; \ | |
153 | int _i; \ | |
154 | \ | |
155 | for (_i = 0; _i < 16; _i++) { \ | |
156 | _x = LOAD32_L(s); (s) += 4; \ | |
157 | _x ^= (a)[_i]; \ | |
158 | STORE32_L((d), _x); (d) += 4; \ | |
159 | } \ | |
160 | } while (0) | |
161 | ||
162 | /* Fill the context @ctx@'s buffer from the matrix @a@ in preparation for | |
163 | * emitting partial blocks of output. | |
164 | */ | |
165 | #define SALSA20_PREPBUF(ctx, a) do { \ | |
166 | int _i; \ | |
167 | for (_i = 0; _i < 16; _i++) STORE32_L((ctx)->buf + 4*_i, (a)[_i]); \ | |
168 | (ctx)->bufi = 0; \ | |
169 | } while (0) | |
170 | ||
171 | /* Write at most @n@ bytes of buffered output from the context @ctx@ to the | |
172 | * output buffer @d@ (if it's not null), XORing it with the input buffer @s@ | |
173 | * (if that's not null). Both @s@ and @d@ are advanced if they aren't null; | |
174 | * @n@ is decreased appropriately. | |
175 | */ | |
176 | #define SALSA20_OUTBUF(ctx, d, s, n) do { \ | |
177 | size_t _n = (n), _left = SALSA20_OUTSZ - (ctx)->bufi; \ | |
178 | if (_n > _left) _n = _left; \ | |
179 | (n) -= _n; \ | |
180 | if (!(d)) (ctx)->bufi += _n; \ | |
181 | else if (s) while (_n--) *(d)++ = (ctx)->buf[(ctx)->bufi++] ^ *(s)++; \ | |
182 | else while (_n--) *(d)++ = (ctx)->buf[(ctx)->bufi++]; \ | |
183 | } while (0) | |
184 | ||
185 | /*----- Variants and naming -----------------------------------------------*/ | |
186 | ||
187 | /* Common numbers of rounds, for which we generate definitions. */ | |
188 | #define SALSA20_VARS(_) _(8) _(12) _(20) | |
189 | ||
190 | /* Constructing externally-facing names. */ | |
191 | #define SALSA20_DECOR(base, r, suff) SALSA20__DECOR_##r(base, suff) | |
192 | #define SALSA20__DECOR_20(base, suff) GLUE(base, suff) | |
193 | #define SALSA20__DECOR_12(base, suff) GLUE(base##12, suff) | |
194 | #define SALSA20__DECOR_8(base, suff) GLUE(base##8, suff) | |
195 | ||
196 | /* Preprocessor-time table of the standard names. */ | |
197 | #define SALSA20_NAME_20 "salsa20" | |
198 | #define SALSA20_NAME_12 "salsa20/12" | |
199 | #define SALSA20_NAME_8 "salsa20/8" | |
200 | ||
201 | /*----- That's all, folks -------------------------------------------------*/ | |
202 | ||
203 | #ifdef __cplusplus | |
204 | } | |
205 | #endif | |
206 | ||
207 | #endif |