Line data Source code
1 : // Copyright (c) 2017-2022 The Bitcoin Core developers
2 : // Distributed under the MIT software license, see the accompanying
3 : // file COPYING or http://www.opensource.org/licenses/mit-license.php.
4 :
5 : #include <crypto/muhash.h>
6 :
7 : #include <crypto/chacha20.h>
8 : #include <crypto/common.h>
9 : #include <hash.h>
10 :
11 : #include <cassert>
12 : #include <cstdio>
13 : #include <limits>
14 :
15 : namespace {
16 :
17 : using limb_t = Num3072::limb_t;
18 : using double_limb_t = Num3072::double_limb_t;
19 : constexpr int LIMB_SIZE = Num3072::LIMB_SIZE;
20 : /** 2^3072 - 1103717, the largest 3072-bit safe prime number, is used as the modulus. */
21 : constexpr limb_t MAX_PRIME_DIFF = 1103717;
22 :
23 : /** Extract the lowest limb of [c0,c1,c2] into n, and left shift the number by 1 limb. */
24 0 : inline void extract3(limb_t& c0, limb_t& c1, limb_t& c2, limb_t& n)
25 : {
26 0 : n = c0;
27 0 : c0 = c1;
28 0 : c1 = c2;
29 0 : c2 = 0;
30 0 : }
31 :
32 : /** [c0,c1] = a * b */
33 0 : inline void mul(limb_t& c0, limb_t& c1, const limb_t& a, const limb_t& b)
34 : {
35 0 : double_limb_t t = (double_limb_t)a * b;
36 0 : c1 = t >> LIMB_SIZE;
37 0 : c0 = t;
38 0 : }
39 :
40 : /* [c0,c1,c2] += n * [d0,d1,d2]. c2 is 0 initially */
41 0 : inline void mulnadd3(limb_t& c0, limb_t& c1, limb_t& c2, limb_t& d0, limb_t& d1, limb_t& d2, const limb_t& n)
42 : {
43 0 : double_limb_t t = (double_limb_t)d0 * n + c0;
44 0 : c0 = t;
45 0 : t >>= LIMB_SIZE;
46 0 : t += (double_limb_t)d1 * n + c1;
47 0 : c1 = t;
48 0 : t >>= LIMB_SIZE;
49 0 : c2 = t + d2 * n;
50 0 : }
51 :
52 : /* [c0,c1] *= n */
53 0 : inline void muln2(limb_t& c0, limb_t& c1, const limb_t& n)
54 : {
55 0 : double_limb_t t = (double_limb_t)c0 * n;
56 0 : c0 = t;
57 0 : t >>= LIMB_SIZE;
58 0 : t += (double_limb_t)c1 * n;
59 0 : c1 = t;
60 0 : }
61 :
62 : /** [c0,c1,c2] += a * b */
63 0 : inline void muladd3(limb_t& c0, limb_t& c1, limb_t& c2, const limb_t& a, const limb_t& b)
64 : {
65 0 : double_limb_t t = (double_limb_t)a * b;
66 0 : limb_t th = t >> LIMB_SIZE;
67 0 : limb_t tl = t;
68 :
69 0 : c0 += tl;
70 0 : th += (c0 < tl) ? 1 : 0;
71 0 : c1 += th;
72 0 : c2 += (c1 < th) ? 1 : 0;
73 0 : }
74 :
75 : /** [c0,c1,c2] += 2 * a * b */
76 0 : inline void muldbladd3(limb_t& c0, limb_t& c1, limb_t& c2, const limb_t& a, const limb_t& b)
77 : {
78 0 : double_limb_t t = (double_limb_t)a * b;
79 0 : limb_t th = t >> LIMB_SIZE;
80 0 : limb_t tl = t;
81 :
82 0 : c0 += tl;
83 0 : limb_t tt = th + ((c0 < tl) ? 1 : 0);
84 0 : c1 += tt;
85 0 : c2 += (c1 < tt) ? 1 : 0;
86 0 : c0 += tl;
87 0 : th += (c0 < tl) ? 1 : 0;
88 0 : c1 += th;
89 0 : c2 += (c1 < th) ? 1 : 0;
90 0 : }
91 :
92 : /**
93 : * Add limb a to [c0,c1]: [c0,c1] += a. Then extract the lowest
94 : * limb of [c0,c1] into n, and left shift the number by 1 limb.
95 : * */
96 0 : inline void addnextract2(limb_t& c0, limb_t& c1, const limb_t& a, limb_t& n)
97 : {
98 0 : limb_t c2 = 0;
99 :
100 : // add
101 0 : c0 += a;
102 0 : if (c0 < a) {
103 0 : c1 += 1;
104 :
105 : // Handle case when c1 has overflown
106 0 : if (c1 == 0)
107 0 : c2 = 1;
108 0 : }
109 :
110 : // extract
111 0 : n = c0;
112 0 : c0 = c1;
113 0 : c1 = c2;
114 0 : }
115 :
116 : /** in_out = in_out^(2^sq) * mul */
117 0 : inline void square_n_mul(Num3072& in_out, const int sq, const Num3072& mul)
118 : {
119 0 : for (int j = 0; j < sq; ++j) in_out.Square();
120 0 : in_out.Multiply(mul);
121 0 : }
122 :
123 : } // namespace
124 :
125 : /** Indicates whether d is larger than the modulus. */
126 0 : bool Num3072::IsOverflow() const
127 : {
128 0 : if (this->limbs[0] <= std::numeric_limits<limb_t>::max() - MAX_PRIME_DIFF) return false;
129 0 : for (int i = 1; i < LIMBS; ++i) {
130 0 : if (this->limbs[i] != std::numeric_limits<limb_t>::max()) return false;
131 0 : }
132 0 : return true;
133 0 : }
134 :
135 0 : void Num3072::FullReduce()
136 : {
137 0 : limb_t c0 = MAX_PRIME_DIFF;
138 0 : limb_t c1 = 0;
139 0 : for (int i = 0; i < LIMBS; ++i) {
140 0 : addnextract2(c0, c1, this->limbs[i], this->limbs[i]);
141 0 : }
142 0 : }
143 :
144 0 : Num3072 Num3072::GetInverse() const
145 : {
146 : // For fast exponentiation a sliding window exponentiation with repunit
147 : // precomputation is utilized. See "Fast Point Decompression for Standard
148 : // Elliptic Curves" (Brumley, Järvinen, 2008).
149 :
150 0 : Num3072 p[12]; // p[i] = a^(2^(2^i)-1)
151 0 : Num3072 out;
152 :
153 0 : p[0] = *this;
154 :
155 0 : for (int i = 0; i < 11; ++i) {
156 0 : p[i + 1] = p[i];
157 0 : for (int j = 0; j < (1 << i); ++j) p[i + 1].Square();
158 0 : p[i + 1].Multiply(p[i]);
159 0 : }
160 :
161 0 : out = p[11];
162 :
163 0 : square_n_mul(out, 512, p[9]);
164 0 : square_n_mul(out, 256, p[8]);
165 0 : square_n_mul(out, 128, p[7]);
166 0 : square_n_mul(out, 64, p[6]);
167 0 : square_n_mul(out, 32, p[5]);
168 0 : square_n_mul(out, 8, p[3]);
169 0 : square_n_mul(out, 2, p[1]);
170 0 : square_n_mul(out, 1, p[0]);
171 0 : square_n_mul(out, 5, p[2]);
172 0 : square_n_mul(out, 3, p[0]);
173 0 : square_n_mul(out, 2, p[0]);
174 0 : square_n_mul(out, 4, p[0]);
175 0 : square_n_mul(out, 4, p[1]);
176 0 : square_n_mul(out, 3, p[0]);
177 :
178 0 : return out;
179 : }
180 :
181 0 : void Num3072::Multiply(const Num3072& a)
182 : {
183 0 : limb_t c0 = 0, c1 = 0, c2 = 0;
184 0 : Num3072 tmp;
185 :
186 : /* Compute limbs 0..N-2 of this*a into tmp, including one reduction. */
187 0 : for (int j = 0; j < LIMBS - 1; ++j) {
188 0 : limb_t d0 = 0, d1 = 0, d2 = 0;
189 0 : mul(d0, d1, this->limbs[1 + j], a.limbs[LIMBS + j - (1 + j)]);
190 0 : for (int i = 2 + j; i < LIMBS; ++i) muladd3(d0, d1, d2, this->limbs[i], a.limbs[LIMBS + j - i]);
191 0 : mulnadd3(c0, c1, c2, d0, d1, d2, MAX_PRIME_DIFF);
192 0 : for (int i = 0; i < j + 1; ++i) muladd3(c0, c1, c2, this->limbs[i], a.limbs[j - i]);
193 0 : extract3(c0, c1, c2, tmp.limbs[j]);
194 0 : }
195 :
196 : /* Compute limb N-1 of a*b into tmp. */
197 0 : assert(c2 == 0);
198 0 : for (int i = 0; i < LIMBS; ++i) muladd3(c0, c1, c2, this->limbs[i], a.limbs[LIMBS - 1 - i]);
199 0 : extract3(c0, c1, c2, tmp.limbs[LIMBS - 1]);
200 :
201 : /* Perform a second reduction. */
202 0 : muln2(c0, c1, MAX_PRIME_DIFF);
203 0 : for (int j = 0; j < LIMBS; ++j) {
204 0 : addnextract2(c0, c1, tmp.limbs[j], this->limbs[j]);
205 0 : }
206 :
207 0 : assert(c1 == 0);
208 0 : assert(c0 == 0 || c0 == 1);
209 :
210 : /* Perform up to two more reductions if the internal state has already
211 : * overflown the MAX of Num3072 or if it is larger than the modulus or
212 : * if both are the case.
213 : * */
214 0 : if (this->IsOverflow()) this->FullReduce();
215 0 : if (c0) this->FullReduce();
216 0 : }
217 :
218 0 : void Num3072::Square()
219 : {
220 0 : limb_t c0 = 0, c1 = 0, c2 = 0;
221 0 : Num3072 tmp;
222 :
223 : /* Compute limbs 0..N-2 of this*this into tmp, including one reduction. */
224 0 : for (int j = 0; j < LIMBS - 1; ++j) {
225 0 : limb_t d0 = 0, d1 = 0, d2 = 0;
226 0 : for (int i = 0; i < (LIMBS - 1 - j) / 2; ++i) muldbladd3(d0, d1, d2, this->limbs[i + j + 1], this->limbs[LIMBS - 1 - i]);
227 0 : if ((j + 1) & 1) muladd3(d0, d1, d2, this->limbs[(LIMBS - 1 - j) / 2 + j + 1], this->limbs[LIMBS - 1 - (LIMBS - 1 - j) / 2]);
228 0 : mulnadd3(c0, c1, c2, d0, d1, d2, MAX_PRIME_DIFF);
229 0 : for (int i = 0; i < (j + 1) / 2; ++i) muldbladd3(c0, c1, c2, this->limbs[i], this->limbs[j - i]);
230 0 : if ((j + 1) & 1) muladd3(c0, c1, c2, this->limbs[(j + 1) / 2], this->limbs[j - (j + 1) / 2]);
231 0 : extract3(c0, c1, c2, tmp.limbs[j]);
232 0 : }
233 :
234 0 : assert(c2 == 0);
235 0 : for (int i = 0; i < LIMBS / 2; ++i) muldbladd3(c0, c1, c2, this->limbs[i], this->limbs[LIMBS - 1 - i]);
236 0 : extract3(c0, c1, c2, tmp.limbs[LIMBS - 1]);
237 :
238 : /* Perform a second reduction. */
239 0 : muln2(c0, c1, MAX_PRIME_DIFF);
240 0 : for (int j = 0; j < LIMBS; ++j) {
241 0 : addnextract2(c0, c1, tmp.limbs[j], this->limbs[j]);
242 0 : }
243 :
244 0 : assert(c1 == 0);
245 0 : assert(c0 == 0 || c0 == 1);
246 :
247 : /* Perform up to two more reductions if the internal state has already
248 : * overflown the MAX of Num3072 or if it is larger than the modulus or
249 : * if both are the case.
250 : * */
251 0 : if (this->IsOverflow()) this->FullReduce();
252 0 : if (c0) this->FullReduce();
253 0 : }
254 :
255 0 : void Num3072::SetToOne()
256 : {
257 0 : this->limbs[0] = 1;
258 0 : for (int i = 1; i < LIMBS; ++i) this->limbs[i] = 0;
259 0 : }
260 :
261 0 : void Num3072::Divide(const Num3072& a)
262 : {
263 0 : if (this->IsOverflow()) this->FullReduce();
264 :
265 0 : Num3072 inv{};
266 0 : if (a.IsOverflow()) {
267 0 : Num3072 b = a;
268 0 : b.FullReduce();
269 0 : inv = b.GetInverse();
270 0 : } else {
271 0 : inv = a.GetInverse();
272 : }
273 :
274 0 : this->Multiply(inv);
275 0 : if (this->IsOverflow()) this->FullReduce();
276 0 : }
277 :
278 0 : Num3072::Num3072(const unsigned char (&data)[BYTE_SIZE]) {
279 0 : for (int i = 0; i < LIMBS; ++i) {
280 : if (sizeof(limb_t) == 4) {
281 : this->limbs[i] = ReadLE32(data + 4 * i);
282 : } else if (sizeof(limb_t) == 8) {
283 0 : this->limbs[i] = ReadLE64(data + 8 * i);
284 : }
285 0 : }
286 0 : }
287 :
288 0 : void Num3072::ToBytes(unsigned char (&out)[BYTE_SIZE]) {
289 0 : for (int i = 0; i < LIMBS; ++i) {
290 : if (sizeof(limb_t) == 4) {
291 : WriteLE32(out + i * 4, this->limbs[i]);
292 : } else if (sizeof(limb_t) == 8) {
293 0 : WriteLE64(out + i * 8, this->limbs[i]);
294 : }
295 0 : }
296 0 : }
297 :
298 0 : Num3072 MuHash3072::ToNum3072(Span<const unsigned char> in) {
299 : unsigned char tmp[Num3072::BYTE_SIZE];
300 :
301 0 : uint256 hashed_in{(HashWriter{} << in).GetSHA256()};
302 : static_assert(sizeof(tmp) % ChaCha20Aligned::BLOCKLEN == 0);
303 0 : ChaCha20Aligned{MakeByteSpan(hashed_in)}.Keystream(MakeWritableByteSpan(tmp));
304 0 : Num3072 out{tmp};
305 :
306 0 : return out;
307 : }
308 :
309 0 : MuHash3072::MuHash3072(Span<const unsigned char> in) noexcept
310 : {
311 0 : m_numerator = ToNum3072(in);
312 0 : }
313 :
314 0 : void MuHash3072::Finalize(uint256& out) noexcept
315 : {
316 0 : m_numerator.Divide(m_denominator);
317 0 : m_denominator.SetToOne(); // Needed to keep the MuHash object valid
318 :
319 : unsigned char data[Num3072::BYTE_SIZE];
320 0 : m_numerator.ToBytes(data);
321 :
322 0 : out = (HashWriter{} << data).GetSHA256();
323 0 : }
324 :
325 0 : MuHash3072& MuHash3072::operator*=(const MuHash3072& mul) noexcept
326 : {
327 0 : m_numerator.Multiply(mul.m_numerator);
328 0 : m_denominator.Multiply(mul.m_denominator);
329 0 : return *this;
330 : }
331 :
332 0 : MuHash3072& MuHash3072::operator/=(const MuHash3072& div) noexcept
333 : {
334 0 : m_numerator.Multiply(div.m_denominator);
335 0 : m_denominator.Multiply(div.m_numerator);
336 0 : return *this;
337 : }
338 :
339 0 : MuHash3072& MuHash3072::Insert(Span<const unsigned char> in) noexcept {
340 0 : m_numerator.Multiply(ToNum3072(in));
341 0 : return *this;
342 : }
343 :
344 0 : MuHash3072& MuHash3072::Remove(Span<const unsigned char> in) noexcept {
345 0 : m_denominator.Multiply(ToNum3072(in));
346 0 : return *this;
347 : }
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