chiark / gitweb /
math/fgoldi.[ch]: Implement the extra operations needed for Ed448.
[catacomb] / math / fgoldi.h
CommitLineData
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1/* -*-c-*-
2 *
3 * Arithmetic in the Goldilocks field GF(2^448 - 2^224 - 1)
4 *
5 * (c) 2017 Straylight/Edgeware
6 */
7
8/*----- Licensing notice --------------------------------------------------*
9 *
10 * This file is part of Catacomb.
11 *
12 * Catacomb is free software; you can redistribute it and/or modify
13 * it under the terms of the GNU Library General Public License as
14 * published by the Free Software Foundation; either version 2 of the
15 * License, or (at your option) any later version.
16 *
17 * Catacomb is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 * GNU Library General Public License for more details.
21 *
22 * You should have received a copy of the GNU Library General Public
23 * License along with Catacomb; if not, write to the Free
24 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
25 * MA 02111-1307, USA.
26 */
27
28#ifndef CATACOMB_FGOLDI_H
29#define CATACOMB_FGOLDI_H
30
31#ifdef __cplusplus
32 extern "C" {
33#endif
34
35/*----- Header files ------------------------------------------------------*/
36
37#include <mLib/bits.h>
38
39#ifndef CATACOMB_QFARITH_H
40# include "qfarith.h"
41#endif
42
43/*----- Data structures ---------------------------------------------------*/
44
45typedef union {
46 int32 p28[16];
47 int16 p12[40];
48} fgoldi;
49
50#if !defined(FGOLDI_IMPL) && defined(HAVE_INT64)
51# define FGOLDI_IMPL 28
52#endif
53
54#ifndef FGOLDI_IMPL
55# define FGOLDI_IMPL 12
56#endif
57
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58#if FGOLDI_IMPL == 28
59 typedef int32 fgoldi_piece;
60#endif
61#if FGOLDI_IMPL == 12
62 typedef int16 fgoldi_piece;
63#endif
64
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65/*----- Functions provided ------------------------------------------------*/
66
67/* --- @fgoldi_load@ --- *
68 *
69 * Arguments: @fgoldi *z@ = where to store the result
70 * @const octet xv[56]@ = source to read
71 *
72 * Returns: ---
73 *
74 * Use: Reads an element of %$\gf{2^{448} - 2^{224} - 19}$% in
75 * external representation from @xv@ and stores it in @z@.
76 *
77 * External representation is little-endian base-256. Some
78 * elements have multiple encodings, which are not produced by
79 * correct software; use of noncanonical encodings is not an
80 * error, and toleration of them is considered a performance
81 * feature.
82 */
83
84extern void fgoldi_load(fgoldi */*z*/, const octet /*xv*/[56]);
85
86/* --- @fgoldi_store@ --- *
87 *
88 * Arguments: @octet zv[56]@ = where to write the result
89 * @const fgoldi *x@ = the field element to write
90 *
91 * Returns: ---
92 *
93 * Use: Stores a field element in the given octet vector in external
94 * representation. A canonical encoding is always stored.
95 */
96
97extern void fgoldi_store(octet /*zv*/[56], const fgoldi */*x*/);
98
99/* --- @fgoldi_set@ --- *
100 *
101 * Arguments: @fgoldi *z@ = where to write the result
102 * @int a@ = a small-ish constant
103 *
104 * Returns: ---
105 *
106 * Use: Sets @z@ to equal @a@.
107 */
108
109extern void fgoldi_set(fgoldi */*x*/, int /*a*/);
110
111/* --- @fgoldi_add@ --- *
112 *
113 * Arguments: @fgoldi *z@ = where to put the result (may alias @x@ or @y@)
114 * @const fgoldi *x, *y@ = two operands
115 *
116 * Returns: ---
117 *
118 * Use: Set @z@ to the sum %$x + y$%.
119 */
120
121extern void fgoldi_add(fgoldi */*z*/,
122 const fgoldi */*x*/, const fgoldi */*y*/);
123
124/* --- @fgoldi_sub@ --- *
125 *
126 * Arguments: @fgoldi *z@ = where to put the result (may alias @x@ or @y@)
127 * @const fgoldi *x, *y@ = two operands
128 *
129 * Returns: ---
130 *
131 * Use: Set @z@ to the difference %$x - y$%.
132 */
133
134extern void fgoldi_sub(fgoldi */*z*/,
135 const fgoldi */*x*/, const fgoldi */*y*/);
136
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137/* --- @fgoldi_neg@ --- *
138 *
139 * Arguments: @fgoldi *z@ = where to put the result (may alias @x@)
140 * @const fgoldi *x@ = an operand
141 *
142 * Returns: ---
143 *
144 * Use: Set @z = -x@.
145 */
146
147extern void fgoldi_neg(fgoldi */*z*/, const fgoldi */*x*/);
148
149/* --- @fgoldi_pick2@ --- *
150 *
151 * Arguments: @fgoldi *z@ = where to put the result (may alias @x@ or @y@)
152 * @const fgoldi *x, *y@ = two operands
153 * @uint32 m@ = a mask
154 *
155 * Returns: ---
156 *
157 * Use: If @m@ is zero, set @z = y@; if @m@ is all-bits-set, then set
158 * @z = x@. If @m@ has some other value, then scramble @z@ in
159 * an unhelpful way.
160 */
161
162extern void fgoldi_pick2(fgoldi */*z*/,
163 const fgoldi */*x*/, const fgoldi */*y*/,
164 uint32 /*m*/);
165
166/* --- @fgoldi_pickn@ --- *
167 *
168 * Arguments: @fgoldi *z@ = where to put the result
169 * @const fgoldi *v@ = a table of entries
170 * @size_t n@ = the number of entries in @v@
171 * @size_t i@ = an index
172 *
173 * Returns: ---
174 *
175 * Use: If @0 <= i < n < 32@ then set @z = v[i]@. If @n >= 32@ then
176 * do something unhelpful; otherwise, if @i >= n@ then set @z@
177 * to zero.
178 */
179
180extern void fgoldi_pickn(fgoldi */*z*/,
181 const fgoldi */*v*/, size_t /*n*/, size_t /*i*/);
182
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183/* --- @fgoldi_condswap@ --- *
184 *
185 * Arguments: @fgoldi *x, *y@ = two operands
186 * @uint32 m@ = a mask
187 *
188 * Returns: ---
189 *
190 * Use: If @m@ is zero, do nothing; if @m@ is all-bits-set, then
191 * exchange @x@ and @y@. If @m@ has some other value, then
192 * scramble @x@ and @y@ in an unhelpful way.
193 */
194
195extern void fgoldi_condswap(fgoldi */*x*/, fgoldi */*y*/, uint32 /*m*/);
196
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197/* --- @fgoldi_condneg@ --- *
198 *
199 * Arguments: @fgoldi *z@ = where to put the result (may alias @x@)
200 * @const fgoldi *x@ = an operand
201 * @uint32 m@ = a mask
202 *
203 * Returns: ---
204 *
205 * Use: If @m@ is zero, set @z = x@; if @m@ is all-bits-set, then set
206 * @z = -x@. If @m@ has some other value then scramble @z@ in
207 * an unhelpful way.
208 */
209
210extern void fgoldi_condneg(fgoldi */*z*/, const fgoldi */*x*/, uint32 /*m*/);
211
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212/* --- @fgoldi_mulconst@ --- *
213 *
214 * Arguments: @fgoldi *z@ = where to put the result (may alias @x@)
215 * @const fgoldi *x@ = an operand
216 * @long a@ = a small-ish constant; %$|a| < 2^{20}$%.
217 *
218 * Returns: ---
219 *
220 * Use: Set @z@ to the product %$a x$%.
221 */
222
223extern void fgoldi_mulconst(fgoldi */*z*/, const fgoldi */*x*/, long /*a*/);
224
225/* --- @fgoldi_mul@ --- *
226 *
227 * Arguments: @fgoldi *z@ = where to put the result (may alias @x@ or @y@)
228 * @const fgoldi *x, *y@ = two operands
229 *
230 * Returns: ---
231 *
232 * Use: Set @z@ to the product %$x y$%.
233 */
234
235extern void fgoldi_mul(fgoldi */*z*/,
236 const fgoldi */*x*/, const fgoldi */*y*/);
237
238/* --- @fgoldi_sqr@ --- *
239 *
240 * Arguments: @fgoldi *z@ = where to put the result (may alias @x@ or @y@)
241 * @const fgoldi *x@ = an operand
242 *
243 * Returns: ---
244 *
245 * Use: Set @z@ to the square %$x^2$%.
246 */
247
248extern void fgoldi_sqr(fgoldi */*z*/, const fgoldi */*x*/);
249
250/* --- @fgoldi_inv@ --- *
251 *
252 * Arguments: @fgoldi *z@ = where to put the result (may alias @x@)
253 * @const fgoldi *x@ = an operand
254 *
255 * Returns: ---
256 *
257 * Use: Stores in @z@ the multiplicative inverse %$x^{-1}$%. If
258 * %$x = 0$% then @z@ is set to zero. This is considered a
259 * feature.
260 */
261
262extern void fgoldi_inv(fgoldi */*z*/, const fgoldi */*x*/);
263
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264/* --- @fgoldi_quosqrt@ --- *
265 *
266 * Arguments: @fgoldi *z@ = where to put the result (may alias @x@ or @y@)
267 * @const fgoldi *x, *y@ = two operands
268 *
269 * Returns: Zero if successful, @-1@ if %$x/y$% is not a square.
270 *
271 * Use: Stores in @z@ the one of the square roots %$\pm\sqrt{x/y}$%.
272 * If %$x = y = 0% then the result is zero; if %$y = 0$% but %$x
273 * \ne 0$% then the operation fails. If you wanted a specific
274 * square root then you'll have to pick it yourself.
275 */
276
277extern int fgoldi_quosqrt(fgoldi */*z*/,
278 const fgoldi */*x*/, const fgoldi */*y*/);
279
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280/*----- That's all, folks -------------------------------------------------*/
281
282#ifdef __cplusplus
283 }
284#endif
285
286#endif