Botan 2.19.5 Crypto and TLS for C&

nistp_redc.cpp
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1/*
2* NIST prime reductions
3* (C) 2014,2015,2018 Jack Lloyd
4*
5* Botan is released under the Simplified BSD License (see license.txt)
6*/
7
8#include <botan/curve_nistp.h>
9#include <botan/internal/mp_core.h>
10#include <botan/internal/mp_asmi.h>
11#include <botan/internal/ct_utils.h>
12
13 namespace Botan {
14
15 const BigInt& prime_p521()
16 {
17 static const BigInt p521("0x1FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF"
18 "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF");
19
20 return p521;
21 }
22
23 void redc_p521(BigInt& x, secure_vector<word>& ws)
24 {
25 const size_t p_full_words = 521 / BOTAN_MP_WORD_BITS;
26 const size_t p_top_bits = 521 % BOTAN_MP_WORD_BITS;
27 const size_t p_words = p_full_words + 1;
28
29#if (BOTAN_MP_WORD_BITS == 64)
30 static const word p521_words[p_words] = {
31 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF,
32 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF,
33 0x1FF };
34#else
35 static const word p521_words[p_words] = {
36 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
37 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
38 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
39 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF,
40 0x1FF };
41#endif
42
43 if(ws.size() < p_words + 1)
44 ws.resize(p_words + 1);
45
46 clear_mem(ws.data(), ws.size());
47 bigint_shr2(ws.data(), x.data(), std::min(x.size(), 2*p_words), p_full_words, p_top_bits);
48
49 x.mask_bits(521);
50 x.grow_to(p_words);
51
52 // Word-level carry will be zero
53 word carry = bigint_add3_nc(x.mutable_data(), x.data(), p_words, ws.data(), p_words);
54 BOTAN_ASSERT_EQUAL(carry, 0, "Final carry in P-521 reduction");
55
56 const word top_word = x.word_at(p_full_words);
57
58 /*
59 * Check if we need to reduce modulo P
60 * There are two possible cases:
61 * - The result overflowed past 521 bits, in which case bit 522 will be set
62 * - The result is exactly 2**521 - 1
63 */
64 const auto bit_522_set = CT::Mask<word>::expand(top_word >> p_top_bits);
65
66 word and_512 = MP_WORD_MAX;
67 for(size_t i = 0; i != p_full_words; ++i)
68 and_512 &= x.word_at(i);
69 const auto all_512_low_bits_set = CT::Mask<word>::is_equal(and_512, MP_WORD_MAX);
70 const auto has_p521_top_word = CT::Mask<word>::is_equal(top_word, 0x1FF);
71 const auto is_p521 = all_512_low_bits_set & has_p521_top_word;
72
73 const auto needs_reduction = is_p521 | bit_522_set;
74
75 bigint_cnd_sub(needs_reduction.value(), x.mutable_data(), p521_words, p_words);
76 }
77
78 namespace {
79
80/**
81* Treating this MPI as a sequence of 32-bit words in big-endian
82* order, return word i. The array is assumed to be large enough.
83*/
84 inline uint32_t get_uint32(const word xw[], size_t i)
85 {
86#if (BOTAN_MP_WORD_BITS == 32)
87 return xw[i];
88#else
89 return static_cast<uint32_t>(xw[i/2] >> ((i % 2)*32));
90#endif
91 }
92
93 inline void set_words(word x[], size_t i, uint32_t R0, uint32_t R1)
94 {
95#if (BOTAN_MP_WORD_BITS == 32)
96 x[i] = R0;
97 x[i+1] = R1;
98#else
99 x[i/2] = (static_cast<uint64_t>(R1) << 32) | R0;
100#endif
101 }
102
103}
104
105 const BigInt& prime_p192()
106 {
107 static const BigInt p192("0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFFFFFFFFFFFF");
108 return p192;
109 }
110
111 void redc_p192(BigInt& x, secure_vector<word>& ws)
112 {
113 BOTAN_UNUSED(ws);
114
115 static const size_t p192_limbs = 192 / BOTAN_MP_WORD_BITS;
116
117 x.grow_to(2*p192_limbs);
118 word* xw = x.mutable_data();
119
120 const uint64_t X00 = get_uint32(xw, 0);
121 const uint64_t X01 = get_uint32(xw, 1);
122 const uint64_t X02 = get_uint32(xw, 2);
123 const uint64_t X03 = get_uint32(xw, 3);
124 const uint64_t X04 = get_uint32(xw, 4);
125 const uint64_t X05 = get_uint32(xw, 5);
126 const uint64_t X06 = get_uint32(xw, 6);
127 const uint64_t X07 = get_uint32(xw, 7);
128 const uint64_t X08 = get_uint32(xw, 8);
129 const uint64_t X09 = get_uint32(xw, 9);
130 const uint64_t X10 = get_uint32(xw, 10);
131 const uint64_t X11 = get_uint32(xw, 11);
132
133 const uint64_t S0 = X00 + X06 + X10;
134 const uint64_t S1 = X01 + X07 + X11;
135 const uint64_t S2 = X02 + X06 + X08 + X10;
136 const uint64_t S3 = X03 + X07 + X09 + X11;
137 const uint64_t S4 = X04 + X08 + X10;
138 const uint64_t S5 = X05 + X09 + X11;
139
140 uint64_t S = 0;
141 uint32_t R0 = 0, R1 = 0;
142
143 S += S0;
144 R0 = static_cast<uint32_t>(S);
145 S >>= 32;
146
147 S += S1;
148 R1 = static_cast<uint32_t>(S);
149 S >>= 32;
150
151 set_words(xw, 0, R0, R1);
152
153 S += S2;
154 R0 = static_cast<uint32_t>(S);
155 S >>= 32;
156
157 S += S3;
158 R1 = static_cast<uint32_t>(S);
159 S >>= 32;
160
161 set_words(xw, 2, R0, R1);
162
163 S += S4;
164 R0 = static_cast<uint32_t>(S);
165 S >>= 32;
166
167 S += S5;
168 R1 = static_cast<uint32_t>(S);
169 S >>= 32;
170
171 set_words(xw, 4, R0, R1);
172
173 // No underflow possible
174
175 /*
176 This is a table of (i*P-192) % 2**192 for i in 1...3
177 */
178 static const word p192_mults[3][p192_limbs] = {
179#if (BOTAN_MP_WORD_BITS == 64)
180 {0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFE, 0xFFFFFFFFFFFFFFFF},
181 {0xFFFFFFFFFFFFFFFE, 0xFFFFFFFFFFFFFFFD, 0xFFFFFFFFFFFFFFFF},
182 {0xFFFFFFFFFFFFFFFD, 0xFFFFFFFFFFFFFFFC, 0xFFFFFFFFFFFFFFFF},
183#else
184 {0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFE, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF},
185 {0xFFFFFFFE, 0xFFFFFFFF, 0xFFFFFFFD, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF},
186 {0xFFFFFFFD, 0xFFFFFFFF, 0xFFFFFFFC, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF},
187#endif
188 };
189
190 CT::unpoison(S);
191 BOTAN_ASSERT(S <= 2, "Expected overflow");
192
193 BOTAN_ASSERT_NOMSG(x.size() >= p192_limbs + 1);
194 x.mask_bits(192);
195 word borrow = bigint_sub2(x.mutable_data(), p192_limbs + 1, p192_mults[S], p192_limbs);
196 BOTAN_DEBUG_ASSERT(borrow == 0 || borrow == 1);
197 bigint_cnd_add(borrow, x.mutable_data(), p192_limbs + 1, p192_mults[0], p192_limbs);
198 }
199
200 const BigInt& prime_p224()
201 {
202 static const BigInt p224("0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF000000000000000000000001");
203 return p224;
204 }
205
206 void redc_p224(BigInt& x, secure_vector<word>& ws)
207 {
208 static const size_t p224_limbs = (BOTAN_MP_WORD_BITS == 32) ? 7 : 4;
209
210 BOTAN_UNUSED(ws);
211
212 x.grow_to(2*p224_limbs);
213 word* xw = x.mutable_data();
214
215 const int64_t X00 = get_uint32(xw, 0);
216 const int64_t X01 = get_uint32(xw, 1);
217 const int64_t X02 = get_uint32(xw, 2);
218 const int64_t X03 = get_uint32(xw, 3);
219 const int64_t X04 = get_uint32(xw, 4);
220 const int64_t X05 = get_uint32(xw, 5);
221 const int64_t X06 = get_uint32(xw, 6);
222 const int64_t X07 = get_uint32(xw, 7);
223 const int64_t X08 = get_uint32(xw, 8);
224 const int64_t X09 = get_uint32(xw, 9);
225 const int64_t X10 = get_uint32(xw, 10);
226 const int64_t X11 = get_uint32(xw, 11);
227 const int64_t X12 = get_uint32(xw, 12);
228 const int64_t X13 = get_uint32(xw, 13);
229
230 // One full copy of P224 is added, so the result is always positive
231
232 const int64_t S0 = 0x00000001 + X00 - X07 - X11;
233 const int64_t S1 = 0x00000000 + X01 - X08 - X12;
234 const int64_t S2 = 0x00000000 + X02 - X09 - X13;
235 const int64_t S3 = 0xFFFFFFFF + X03 + X07 + X11 - X10;
236 const int64_t S4 = 0xFFFFFFFF + X04 + X08 + X12 - X11;
237 const int64_t S5 = 0xFFFFFFFF + X05 + X09 + X13 - X12;
238 const int64_t S6 = 0xFFFFFFFF + X06 + X10 - X13;
239
240 int64_t S = 0;
241 uint32_t R0 = 0, R1 = 0;
242
243 S += S0;
244 R0 = static_cast<uint32_t>(S);
245 S >>= 32;
246
247 S += S1;
248 R1 = static_cast<uint32_t>(S);
249 S >>= 32;
250
251 set_words(xw, 0, R0, R1);
252
253 S += S2;
254 R0 = static_cast<uint32_t>(S);
255 S >>= 32;
256
257 S += S3;
258 R1 = static_cast<uint32_t>(S);
259 S >>= 32;
260
261 set_words(xw, 2, R0, R1);
262
263 S += S4;
264 R0 = static_cast<uint32_t>(S);
265 S >>= 32;
266
267 S += S5;
268 R1 = static_cast<uint32_t>(S);
269 S >>= 32;
270
271 set_words(xw, 4, R0, R1);
272
273 S += S6;
274 R0 = static_cast<uint32_t>(S);
275 S >>= 32;
276
277 set_words(xw, 6, R0, 0);
278
279 static const word p224_mults[3][p224_limbs] = {
280#if (BOTAN_MP_WORD_BITS == 64)
281 {0x0000000000000001, 0xFFFFFFFF00000000, 0xFFFFFFFFFFFFFFFF, 0x00000000FFFFFFFF},
282 {0x0000000000000002, 0xFFFFFFFE00000000, 0xFFFFFFFFFFFFFFFF, 0x00000000FFFFFFFF},
283 {0x0000000000000003, 0xFFFFFFFD00000000, 0xFFFFFFFFFFFFFFFF, 0x00000000FFFFFFFF},
284#else
285 {0x00000001, 0x00000000, 0x00000000, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF},
286 {0x00000002, 0x00000000, 0x00000000, 0xFFFFFFFE, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF},
287 {0x00000003, 0x00000000, 0x00000000, 0xFFFFFFFD, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF}
288#endif
289
290 };
291
292 CT::unpoison(S);
293 BOTAN_ASSERT(S >= 0 && S <= 2, "Expected overflow");
294
295 BOTAN_ASSERT_NOMSG(x.size() >= p224_limbs + 1);
296 x.mask_bits(224);
297 word borrow = bigint_sub2(x.mutable_data(), p224_limbs + 1, p224_mults[S], p224_limbs);
298 BOTAN_DEBUG_ASSERT(borrow == 0 || borrow == 1);
299 bigint_cnd_add(borrow, x.mutable_data(), p224_limbs + 1, p224_mults[0], p224_limbs);
300 }
301
302 const BigInt& prime_p256()
303 {
304 static const BigInt p256("0xFFFFFFFF00000001000000000000000000000000FFFFFFFFFFFFFFFFFFFFFFFF");
305 return p256;
306 }
307
308 void redc_p256(BigInt& x, secure_vector<word>& ws)
309 {
310 static const size_t p256_limbs = (BOTAN_MP_WORD_BITS == 32) ? 8 : 4;
311
312 BOTAN_UNUSED(ws);
313
314 x.grow_to(2*p256_limbs);
315 word* xw = x.mutable_data();
316
317 const int64_t X00 = get_uint32(xw, 0);
318 const int64_t X01 = get_uint32(xw, 1);
319 const int64_t X02 = get_uint32(xw, 2);
320 const int64_t X03 = get_uint32(xw, 3);
321 const int64_t X04 = get_uint32(xw, 4);
322 const int64_t X05 = get_uint32(xw, 5);
323 const int64_t X06 = get_uint32(xw, 6);
324 const int64_t X07 = get_uint32(xw, 7);
325 const int64_t X08 = get_uint32(xw, 8);
326 const int64_t X09 = get_uint32(xw, 9);
327 const int64_t X10 = get_uint32(xw, 10);
328 const int64_t X11 = get_uint32(xw, 11);
329 const int64_t X12 = get_uint32(xw, 12);
330 const int64_t X13 = get_uint32(xw, 13);
331 const int64_t X14 = get_uint32(xw, 14);
332 const int64_t X15 = get_uint32(xw, 15);
333
334 // Adds 6 * P-256 to prevent underflow
335 const int64_t S0 = 0xFFFFFFFA + X00 + X08 + X09 - (X11 + X12 + X13) - X14;
336 const int64_t S1 = 0xFFFFFFFF + X01 + X09 + X10 - X12 - (X13 + X14 + X15);
337 const int64_t S2 = 0xFFFFFFFF + X02 + X10 + X11 - (X13 + X14 + X15);
338 const int64_t S3 = 0x00000005 + X03 + (X11 + X12)*2 + X13 - X15 - X08 - X09;
339 const int64_t S4 = 0x00000000 + X04 + (X12 + X13)*2 + X14 - X09 - X10;
340 const int64_t S5 = 0x00000000 + X05 + (X13 + X14)*2 + X15 - X10 - X11;
341 const int64_t S6 = 0x00000006 + X06 + X13 + X14*3 + X15*2 - X08 - X09;
342 const int64_t S7 = 0xFFFFFFFA + X07 + X15*3 + X08 - X10 - (X11 + X12 + X13);
343
344 int64_t S = 0;
345
346 uint32_t R0 = 0, R1 = 0;
347
348 S += S0;
349 R0 = static_cast<uint32_t>(S);
350 S >>= 32;
351
352 S += S1;
353 R1 = static_cast<uint32_t>(S);
354 S >>= 32;
355
356 set_words(xw, 0, R0, R1);
357
358 S += S2;
359 R0 = static_cast<uint32_t>(S);
360 S >>= 32;
361
362 S += S3;
363 R1 = static_cast<uint32_t>(S);
364 S >>= 32;
365
366 set_words(xw, 2, R0, R1);
367
368 S += S4;
369 R0 = static_cast<uint32_t>(S);
370 S >>= 32;
371
372 S += S5;
373 R1 = static_cast<uint32_t>(S);
374 S >>= 32;
375
376 set_words(xw, 4, R0, R1);
377
378 S += S6;
379 R0 = static_cast<uint32_t>(S);
380 S >>= 32;
381
382 S += S7;
383 R1 = static_cast<uint32_t>(S);
384 S >>= 32;
385 set_words(xw, 6, R0, R1);
386
387 S += 5; // the top digits of 6*P-256
388
389 /*
390 This is a table of (i*P-256) % 2**256 for i in 1...10
391 */
392 static const word p256_mults[11][p256_limbs] = {
393#if (BOTAN_MP_WORD_BITS == 64)
394 {0xFFFFFFFFFFFFFFFF, 0x00000000FFFFFFFF, 0x0000000000000000, 0xFFFFFFFF00000001},
395 {0xFFFFFFFFFFFFFFFE, 0x00000001FFFFFFFF, 0x0000000000000000, 0xFFFFFFFE00000002},
396 {0xFFFFFFFFFFFFFFFD, 0x00000002FFFFFFFF, 0x0000000000000000, 0xFFFFFFFD00000003},
397 {0xFFFFFFFFFFFFFFFC, 0x00000003FFFFFFFF, 0x0000000000000000, 0xFFFFFFFC00000004},
398 {0xFFFFFFFFFFFFFFFB, 0x00000004FFFFFFFF, 0x0000000000000000, 0xFFFFFFFB00000005},
399 {0xFFFFFFFFFFFFFFFA, 0x00000005FFFFFFFF, 0x0000000000000000, 0xFFFFFFFA00000006},
400 {0xFFFFFFFFFFFFFFF9, 0x00000006FFFFFFFF, 0x0000000000000000, 0xFFFFFFF900000007},
401 {0xFFFFFFFFFFFFFFF8, 0x00000007FFFFFFFF, 0x0000000000000000, 0xFFFFFFF800000008},
402 {0xFFFFFFFFFFFFFFF7, 0x00000008FFFFFFFF, 0x0000000000000000, 0xFFFFFFF700000009},
403 {0xFFFFFFFFFFFFFFF6, 0x00000009FFFFFFFF, 0x0000000000000000, 0xFFFFFFF60000000A},
404 {0xFFFFFFFFFFFFFFF5, 0x0000000AFFFFFFFF, 0x0000000000000000, 0xFFFFFFF50000000B},
405#else
406 {0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000000, 0x00000000, 0x00000000, 0x00000001, 0xFFFFFFFF},
407 {0xFFFFFFFE, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000001, 0x00000000, 0x00000000, 0x00000002, 0xFFFFFFFE},
408 {0xFFFFFFFD, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000002, 0x00000000, 0x00000000, 0x00000003, 0xFFFFFFFD},
409 {0xFFFFFFFC, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000003, 0x00000000, 0x00000000, 0x00000004, 0xFFFFFFFC},
410 {0xFFFFFFFB, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000004, 0x00000000, 0x00000000, 0x00000005, 0xFFFFFFFB},
411 {0xFFFFFFFA, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000005, 0x00000000, 0x00000000, 0x00000006, 0xFFFFFFFA},
412 {0xFFFFFFF9, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000006, 0x00000000, 0x00000000, 0x00000007, 0xFFFFFFF9},
413 {0xFFFFFFF8, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000007, 0x00000000, 0x00000000, 0x00000008, 0xFFFFFFF8},
414 {0xFFFFFFF7, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000008, 0x00000000, 0x00000000, 0x00000009, 0xFFFFFFF7},
415 {0xFFFFFFF6, 0xFFFFFFFF, 0xFFFFFFFF, 0x00000009, 0x00000000, 0x00000000, 0x0000000A, 0xFFFFFFF6},
416 {0xFFFFFFF5, 0xFFFFFFFF, 0xFFFFFFFF, 0x0000000A, 0x00000000, 0x00000000, 0x0000000B, 0xFFFFFFF5},
417#endif
418 };
419
420 CT::unpoison(S);
421 BOTAN_ASSERT(S >= 0 && S <= 10, "Expected overflow");
422
423 BOTAN_ASSERT_NOMSG(x.size() >= p256_limbs + 1);
424 x.mask_bits(256);
425 word borrow = bigint_sub2(x.mutable_data(), p256_limbs + 1, p256_mults[S], p256_limbs);
426 BOTAN_DEBUG_ASSERT(borrow == 0 || borrow == 1);
427 bigint_cnd_add(borrow, x.mutable_data(), p256_limbs + 1, p256_mults[0], p256_limbs);
428 }
429
430 const BigInt& prime_p384()
431 {
432 static const BigInt p384("0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEFFFFFFFF0000000000000000FFFFFFFF");
433 return p384;
434 }
435
436 void redc_p384(BigInt& x, secure_vector<word>& ws)
437 {
438 BOTAN_UNUSED(ws);
439
440 static const size_t p384_limbs = (BOTAN_MP_WORD_BITS == 32) ? 12 : 6;
441
442 x.grow_to(2*p384_limbs);
443 word* xw = x.mutable_data();
444
445 const int64_t X00 = get_uint32(xw, 0);
446 const int64_t X01 = get_uint32(xw, 1);
447 const int64_t X02 = get_uint32(xw, 2);
448 const int64_t X03 = get_uint32(xw, 3);
449 const int64_t X04 = get_uint32(xw, 4);
450 const int64_t X05 = get_uint32(xw, 5);
451 const int64_t X06 = get_uint32(xw, 6);
452 const int64_t X07 = get_uint32(xw, 7);
453 const int64_t X08 = get_uint32(xw, 8);
454 const int64_t X09 = get_uint32(xw, 9);
455 const int64_t X10 = get_uint32(xw, 10);
456 const int64_t X11 = get_uint32(xw, 11);
457 const int64_t X12 = get_uint32(xw, 12);
458 const int64_t X13 = get_uint32(xw, 13);
459 const int64_t X14 = get_uint32(xw, 14);
460 const int64_t X15 = get_uint32(xw, 15);
461 const int64_t X16 = get_uint32(xw, 16);
462 const int64_t X17 = get_uint32(xw, 17);
463 const int64_t X18 = get_uint32(xw, 18);
464 const int64_t X19 = get_uint32(xw, 19);
465 const int64_t X20 = get_uint32(xw, 20);
466 const int64_t X21 = get_uint32(xw, 21);
467 const int64_t X22 = get_uint32(xw, 22);
468 const int64_t X23 = get_uint32(xw, 23);
469
470 // One copy of P-384 is added to prevent underflow
471 const int64_t S0 = 0xFFFFFFFF + X00 + X12 + X20 + X21 - X23;
472 const int64_t S1 = 0x00000000 + X01 + X13 + X22 + X23 - X12 - X20;
473 const int64_t S2 = 0x00000000 + X02 + X14 + X23 - X13 - X21;
474 const int64_t S3 = 0xFFFFFFFF + X03 + X12 + X15 + X20 + X21 - X14 - X22 - X23;
475 const int64_t S4 = 0xFFFFFFFE + X04 + X12 + X13 + X16 + X20 + X21*2 + X22 - X15 - X23*2;
476 const int64_t S5 = 0xFFFFFFFF + X05 + X13 + X14 + X17 + X21 + X22*2 + X23 - X16;
477 const int64_t S6 = 0xFFFFFFFF + X06 + X14 + X15 + X18 + X22 + X23*2 - X17;
478 const int64_t S7 = 0xFFFFFFFF + X07 + X15 + X16 + X19 + X23 - X18;
479 const int64_t S8 = 0xFFFFFFFF + X08 + X16 + X17 + X20 - X19;
480 const int64_t S9 = 0xFFFFFFFF + X09 + X17 + X18 + X21 - X20;
481 const int64_t SA = 0xFFFFFFFF + X10 + X18 + X19 + X22 - X21;
482 const int64_t SB = 0xFFFFFFFF + X11 + X19 + X20 + X23 - X22;
483
484 int64_t S = 0;
485
486 uint32_t R0 = 0, R1 = 0;
487
488 S += S0;
489 R0 = static_cast<uint32_t>(S);
490 S >>= 32;
491
492 S += S1;
493 R1 = static_cast<uint32_t>(S);
494 S >>= 32;
495
496 set_words(xw, 0, R0, R1);
497
498 S += S2;
499 R0 = static_cast<uint32_t>(S);
500 S >>= 32;
501
502 S += S3;
503 R1 = static_cast<uint32_t>(S);
504 S >>= 32;
505
506 set_words(xw, 2, R0, R1);
507
508 S += S4;
509 R0 = static_cast<uint32_t>(S);
510 S >>= 32;
511
512 S += S5;
513 R1 = static_cast<uint32_t>(S);
514 S >>= 32;
515
516 set_words(xw, 4, R0, R1);
517
518 S += S6;
519 R0 = static_cast<uint32_t>(S);
520 S >>= 32;
521
522 S += S7;
523 R1 = static_cast<uint32_t>(S);
524 S >>= 32;
525
526 set_words(xw, 6, R0, R1);
527
528 S += S8;
529 R0 = static_cast<uint32_t>(S);
530 S >>= 32;
531
532 S += S9;
533 R1 = static_cast<uint32_t>(S);
534 S >>= 32;
535
536 set_words(xw, 8, R0, R1);
537
538 S += SA;
539 R0 = static_cast<uint32_t>(S);
540 S >>= 32;
541
542 S += SB;
543 R1 = static_cast<uint32_t>(S);
544 S >>= 32;
545
546 set_words(xw, 10, R0, R1);
547
548 /*
549 This is a table of (i*P-384) % 2**384 for i in 1...4
550 */
551 static const word p384_mults[5][p384_limbs] = {
552#if (BOTAN_MP_WORD_BITS == 64)
553 {0x00000000FFFFFFFF, 0xFFFFFFFF00000000, 0xFFFFFFFFFFFFFFFE, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF},
554 {0x00000001FFFFFFFE, 0xFFFFFFFE00000000, 0xFFFFFFFFFFFFFFFD, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF},
555 {0x00000002FFFFFFFD, 0xFFFFFFFD00000000, 0xFFFFFFFFFFFFFFFC, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF},
556 {0x00000003FFFFFFFC, 0xFFFFFFFC00000000, 0xFFFFFFFFFFFFFFFB, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF},
557 {0x00000004FFFFFFFB, 0xFFFFFFFB00000000, 0xFFFFFFFFFFFFFFFA, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF, 0xFFFFFFFFFFFFFFFF},
558
559#else
560 {0xFFFFFFFF, 0x00000000, 0x00000000, 0xFFFFFFFF, 0xFFFFFFFE, 0xFFFFFFFF,
561 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF},
562 {0xFFFFFFFE, 0x00000001, 0x00000000, 0xFFFFFFFE, 0xFFFFFFFD, 0xFFFFFFFF,
563 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF},
564 {0xFFFFFFFD, 0x00000002, 0x00000000, 0xFFFFFFFD, 0xFFFFFFFC, 0xFFFFFFFF,
565 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF},
566 {0xFFFFFFFC, 0x00000003, 0x00000000, 0xFFFFFFFC, 0xFFFFFFFB, 0xFFFFFFFF,
567 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF},
568 {0xFFFFFFFB, 0x00000004, 0x00000000, 0xFFFFFFFB, 0xFFFFFFFA, 0xFFFFFFFF,
569 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF, 0xFFFFFFFF},
570#endif
571 };
572
573 CT::unpoison(S);
574 BOTAN_ASSERT(S >= 0 && S <= 4, "Expected overflow");
575
576 BOTAN_ASSERT_NOMSG(x.size() >= p384_limbs + 1);
577 x.mask_bits(384);
578 word borrow = bigint_sub2(x.mutable_data(), p384_limbs + 1, p384_mults[S], p384_limbs);
579 BOTAN_DEBUG_ASSERT(borrow == 0 || borrow == 1);
580 bigint_cnd_add(borrow, x.mutable_data(), p384_limbs + 1, p384_mults[0], p384_limbs);
581 }
582
583}
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#define BOTAN_ASSERT_NOMSG(expr)
Definition: assert.h:68
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Definition: alg_id.cpp:13
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