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0bcb8184 MW |
1 | /* |
2 | * f25519.h: arithmetic modulo 2^255 - 19 | |
3 | */ | |
4 | /* | |
5 | * This file is Free Software. It has been modified to as part of its | |
6 | * incorporation into secnet. | |
7 | * | |
8 | * Copyright 2017 Mark Wooding | |
9 | * | |
10 | * You may redistribute this file and/or modify it under the terms of | |
11 | * the permissive licence shown below. | |
12 | * | |
13 | * You may redistribute secnet as a whole and/or modify it under the | |
14 | * terms of the GNU General Public License as published by the Free | |
15 | * Software Foundation; either version 3, or (at your option) any | |
16 | * later version. | |
17 | * | |
18 | * This program is distributed in the hope that it will be useful, | |
19 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
20 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
21 | * GNU General Public License for more details. | |
22 | * | |
23 | * You should have received a copy of the GNU General Public License | |
24 | * along with this program; if not, see | |
25 | * https://www.gnu.org/licenses/gpl.html. | |
26 | */ | |
27 | /* | |
28 | * Imported from Catacomb, and lightly modified for Secnet (2017-04-30): | |
29 | * | |
30 | * * Use `fake-mLib-bits.h' in place of the real <mLib/bits.h>. | |
31 | * | |
32 | * * Remove the 16/32-bit implementation, since C99 always has 64-bit | |
33 | * arithmetic. | |
34 | * | |
35 | * * Disable some of the operations which aren't needed for X25519. | |
36 | * (They're used for Ed25519, which we don't need.) | |
37 | * | |
38 | * The file's original comment headers are preserved below. | |
39 | */ | |
b7a5ecfc MW |
40 | /* -*-c-*- |
41 | * | |
42 | * Arithmetic modulo 2^255 - 19 | |
43 | * | |
44 | * (c) 2017 Straylight/Edgeware | |
45 | */ | |
46 | ||
47 | /*----- Licensing notice --------------------------------------------------* | |
48 | * | |
49 | * This file is part of Catacomb. | |
50 | * | |
51 | * Catacomb is free software; you can redistribute it and/or modify | |
52 | * it under the terms of the GNU Library General Public License as | |
53 | * published by the Free Software Foundation; either version 2 of the | |
54 | * License, or (at your option) any later version. | |
55 | * | |
56 | * Catacomb is distributed in the hope that it will be useful, | |
57 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
58 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
59 | * GNU Library General Public License for more details. | |
60 | * | |
61 | * You should have received a copy of the GNU Library General Public | |
62 | * License along with Catacomb; if not, write to the Free | |
63 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
64 | * MA 02111-1307, USA. | |
65 | */ | |
66 | ||
67 | #ifndef CATACOMB_F25519_H | |
68 | #define CATACOMB_F25519_H | |
69 | ||
70 | #ifdef __cplusplus | |
71 | extern "C" { | |
72 | #endif | |
73 | ||
74 | /*----- Header files ------------------------------------------------------*/ | |
75 | ||
0bcb8184 | 76 | #include "fake-mLib-bits.h" |
b7a5ecfc MW |
77 | |
78 | #ifndef CATACOMB_QFARITH_H | |
79 | # include "qfarith.h" | |
80 | #endif | |
81 | ||
82 | /*----- Data structures ---------------------------------------------------*/ | |
83 | ||
84 | typedef union { | |
85 | int32 p26[10]; | |
b7a5ecfc MW |
86 | } f25519; |
87 | ||
b7a5ecfc MW |
88 | /*----- Functions provided ------------------------------------------------*/ |
89 | ||
0bcb8184 MW |
90 | #define F25519_TRIM_X25519 |
91 | ||
b7a5ecfc MW |
92 | /* --- @f25519_set@ --- * |
93 | * | |
94 | * Arguments: @f25519 *z@ = where to write the result | |
95 | * @int a@ = a small-ish constant | |
96 | * | |
97 | * Returns: --- | |
98 | * | |
99 | * Use: Sets @z@ to equal @a@. | |
100 | */ | |
101 | ||
102 | extern void f25519_set(f25519 */*x*/, int /*a*/); | |
103 | ||
104 | /* --- @f25519_load@ --- * | |
105 | * | |
106 | * Arguments: @f25519 *z@ = where to store the result | |
107 | * @const octet xv[32]@ = source to read | |
108 | * | |
109 | * Returns: --- | |
110 | * | |
111 | * Use: Reads an element of %$\gf{2^{255} - 19}$% in external | |
112 | * representation from @xv@ and stores it in @z@. | |
113 | * | |
114 | * External representation is little-endian base-256. Elements | |
115 | * have multiple encodings, which are not produced by correct | |
116 | * software; use of noncanonical encodings is not an error, and | |
117 | * toleration of them is considered a performance feature. | |
118 | * | |
119 | * Some specifications, e.g., RFC7748, require the topmost bit | |
120 | * (i.e., bit 7 of @wv[31]@) to be ignored. Callers | |
121 | * implementing such specifications should clear the bit | |
122 | * explicitly. (It's much easier for a caller who wants the bit | |
123 | * to be ignored to clear it than for a caller who wants the bit | |
124 | * to be significant to apply the necessary change by hand.) | |
125 | */ | |
126 | ||
127 | extern void f25519_load(f25519 */*z*/, const octet /*xv*/[32]); | |
128 | ||
129 | /* --- @f25519_store@ --- * | |
130 | * | |
131 | * Arguments: @octet zv[32]@ = where to write the result | |
132 | * @const f25519 *x@ = the field element to write | |
133 | * | |
134 | * Returns: --- | |
135 | * | |
136 | * Use: Stores a field element in the given octet vector in external | |
137 | * representation. A canonical encoding is always stored, so, | |
138 | * in particular, the top bit of @xv[31]@ is always left clear. | |
139 | */ | |
140 | ||
141 | extern void f25519_store(octet /*zv*/[32], const f25519 */*x*/); | |
142 | ||
0bcb8184 MW |
143 | #ifndef F25519_TRIM_X25519 |
144 | ||
b7a5ecfc MW |
145 | /* --- @f25519_pick2@ --- * |
146 | * | |
147 | * Arguments: @f25519 *z@ = where to put the result (may alias @x@ or @y@) | |
148 | * @const f25519 *x, *y@ = two operands | |
149 | * @uint32 m@ = a mask | |
150 | * | |
151 | * Returns: --- | |
152 | * | |
153 | * Use: If @m@ is zero, set @z = y@; if @m@ is all-bits-set, then set | |
154 | * @z = x@. If @m@ has some other value, then scramble @z@ in | |
155 | * an unhelpful way. | |
156 | */ | |
157 | ||
158 | extern void f25519_pick2(f25519 */*z*/, const f25519 */*x*/, | |
159 | const f25519 */*y*/, uint32 /*m*/); | |
160 | ||
161 | /* --- @f25519_pickn@ --- * | |
162 | * | |
163 | * Arguments: @f25519 *z@ = where to put the result | |
164 | * @const f25519 *v@ = a table of entries | |
165 | * @size_t n@ = the number of entries in @v@ | |
166 | * @size_t i@ = an index | |
167 | * | |
168 | * Returns: --- | |
169 | * | |
170 | * Use: If @0 <= i < n < 32@ then set @z = v[i]@. If @n >= 32@ then | |
171 | * do something unhelpful; otherwise, if @i >= n@ then set @z@ | |
172 | * to zero. | |
173 | */ | |
174 | ||
175 | extern void f25519_pickn(f25519 */*z*/, const f25519 */*v*/, size_t /*n*/, | |
176 | size_t /*i*/); | |
177 | ||
0bcb8184 MW |
178 | #endif |
179 | ||
b7a5ecfc MW |
180 | /* --- @f25519_condswap@ --- * |
181 | * | |
182 | * Arguments: @f25519 *x, *y@ = two operands | |
183 | * @uint32 m@ = a mask | |
184 | * | |
185 | * Returns: --- | |
186 | * | |
187 | * Use: If @m@ is zero, do nothing; if @m@ is all-bits-set, then | |
188 | * exchange @x@ and @y@. If @m@ has some other value, then | |
189 | * scramble @x@ and @y@ in an unhelpful way. | |
190 | */ | |
191 | ||
192 | extern void f25519_condswap(f25519 */*x*/, f25519 */*y*/, uint32 /*m*/); | |
193 | ||
194 | /* --- @f25519_add@ --- * | |
195 | * | |
196 | * Arguments: @f25519 *z@ = where to put the result (may alias @x@ or @y@) | |
197 | * @const f25519 *x, *y@ = two operands | |
198 | * | |
199 | * Returns: --- | |
200 | * | |
201 | * Use: Set @z@ to the sum %$x + y$%. | |
202 | */ | |
203 | ||
204 | extern void f25519_add(f25519 */*z*/, | |
205 | const f25519 */*x*/, const f25519 */*y*/); | |
206 | ||
207 | /* --- @f25519_sub@ --- * | |
208 | * | |
209 | * Arguments: @f25519 *z@ = where to put the result (may alias @x@ or @y@) | |
210 | * @const f25519 *x, *y@ = two operands | |
211 | * | |
212 | * Returns: --- | |
213 | * | |
214 | * Use: Set @z@ to the difference %$x - y$%. | |
215 | */ | |
216 | ||
217 | extern void f25519_sub(f25519 */*z*/, | |
218 | const f25519 */*x*/, const f25519 */*y*/); | |
219 | ||
0bcb8184 MW |
220 | #ifndef F25519_TRIM_X25519 |
221 | ||
b7a5ecfc MW |
222 | /* --- @f25519_neg@ --- * |
223 | * | |
224 | * Arguments: @f25519 *z@ = where to put the result (may alias @x@) | |
225 | * @const f25519 *x@ = an operand | |
226 | * | |
227 | * Returns: --- | |
228 | * | |
229 | * Use: Set @z = -x@. | |
230 | */ | |
231 | ||
232 | extern void f25519_neg(f25519 */*z*/, const f25519 */*x*/); | |
233 | ||
234 | /* --- @f25519_condneg@ --- * | |
235 | * | |
236 | * Arguments: @f25519 *z@ = where to put the result (may alias @x@) | |
237 | * @const f25519 *x@ = an operand | |
238 | * @uint32 m@ = a mask | |
239 | * | |
240 | * Returns: --- | |
241 | * | |
242 | * Use: If @m@ is zero, set @z = x@; if @m@ is all-bits-set, then set | |
243 | * @z = -x@. If @m@ has some other value then scramble @z@ in | |
244 | * an unhelpful way. | |
245 | */ | |
246 | ||
247 | extern void f25519_condneg(f25519 */*z*/, const f25519 */*x*/, uint32 /*m*/); | |
248 | ||
0bcb8184 MW |
249 | #endif |
250 | ||
b7a5ecfc MW |
251 | /* --- @f25519_mulconst@ --- * |
252 | * | |
253 | * Arguments: @f25519 *z@ = where to put the result (may alias @x@) | |
254 | * @const f25519 *x@ = an operand | |
255 | * @long a@ = a small-ish constant; %$|a| < 2^{20}$%. | |
256 | * | |
257 | * Returns: --- | |
258 | * | |
259 | * Use: Set @z@ to the product %$a x$%. | |
260 | */ | |
261 | ||
262 | extern void f25519_mulconst(f25519 */*z*/, const f25519 */*x*/, long /*a*/); | |
263 | ||
264 | /* --- @f25519_mul@ --- * | |
265 | * | |
266 | * Arguments: @f25519 *z@ = where to put the result (may alias @x@ or @y@) | |
267 | * @const f25519 *x, *y@ = two operands | |
268 | * | |
269 | * Returns: --- | |
270 | * | |
271 | * Use: Set @z@ to the product %$x y$%. | |
272 | */ | |
273 | ||
274 | extern void f25519_mul(f25519 */*z*/, | |
275 | const f25519 */*x*/, const f25519 */*y*/); | |
276 | ||
277 | /* --- @f25519_sqr@ --- * | |
278 | * | |
279 | * Arguments: @f25519 *z@ = where to put the result (may alias @x@ or @y@) | |
280 | * @const f25519 *x@ = an operand | |
281 | * | |
282 | * Returns: --- | |
283 | * | |
284 | * Use: Set @z@ to the square %$x^2$%. | |
285 | */ | |
286 | ||
287 | extern void f25519_sqr(f25519 */*z*/, const f25519 */*x*/); | |
288 | ||
289 | /* --- @f25519_inv@ --- * | |
290 | * | |
291 | * Arguments: @f25519 *z@ = where to put the result (may alias @x@) | |
292 | * @const f25519 *x@ = an operand | |
293 | * | |
294 | * Returns: --- | |
295 | * | |
296 | * Use: Stores in @z@ the multiplicative inverse %$x^{-1}$%. If | |
297 | * %$x = 0$% then @z@ is set to zero. This is considered a | |
298 | * feature. | |
299 | */ | |
300 | ||
301 | extern void f25519_inv(f25519 */*z*/, const f25519 */*x*/); | |
302 | ||
0bcb8184 MW |
303 | #ifndef F25519_TRIM_X25519 |
304 | ||
b7a5ecfc MW |
305 | /* --- @f25519_quosqrt@ --- * |
306 | * | |
307 | * Arguments: @f25519 *z@ = where to put the result (may alias @x@ or @y@) | |
308 | * @const f25519 *x, *y@ = two operands | |
309 | * | |
310 | * Returns: Zero if successful, @-1@ if %$x/y$% is not a square. | |
311 | * | |
312 | * Use: Stores in @z@ the one of the square roots %$\pm\sqrt{x/y}$%. | |
313 | * If %$x = y = 0% then the result is zero; if %$y = 0$% but %$x | |
314 | * \ne 0$% then the operation fails. If you wanted a specific | |
315 | * square root then you'll have to pick it yourself. | |
316 | */ | |
317 | ||
318 | extern int f25519_quosqrt(f25519 */*z*/, | |
319 | const f25519 */*x*/, const f25519 */*y*/); | |
320 | ||
0bcb8184 MW |
321 | #endif |
322 | ||
b7a5ecfc MW |
323 | /*----- That's all, folks -------------------------------------------------*/ |
324 | ||
325 | #ifdef __cplusplus | |
326 | } | |
327 | #endif | |
328 | ||
329 | #endif |