1 /* 2 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org> 3 * 4 * Permission is hereby granted, free of charge, to any person obtaining 5 * a copy of this software and associated documentation files (the 6 * "Software"), to deal in the Software without restriction, including 7 * without limitation the rights to use, copy, modify, merge, publish, 8 * distribute, sublicense, and/or sell copies of the Software, and to 9 * permit persons to whom the Software is furnished to do so, subject to 10 * the following conditions: 11 * 12 * The above copyright notice and this permission notice shall be 13 * included in all copies or substantial portions of the Software. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN 20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 22 * SOFTWARE. 23 */ 24 25 #include "inner.h" 26 27 /* see inner.h */ 28 void 29 br_i32_montymul(uint32_t *d, const uint32_t *x, const uint32_t *y, 30 const uint32_t *m, uint32_t m0i) 31 { 32 size_t len, u, v; 33 uint64_t dh; 34 35 len = (m[0] + 31) >> 5; 36 br_i32_zero(d, m[0]); 37 dh = 0; 38 for (u = 0; u < len; u ++) { 39 uint32_t f, xu; 40 uint64_t r1, r2, zh; 41 42 xu = x[u + 1]; 43 f = (d[1] + x[u + 1] * y[1]) * m0i; 44 r1 = 0; 45 r2 = 0; 46 for (v = 0; v < len; v ++) { 47 uint64_t z; 48 uint32_t t; 49 50 z = (uint64_t)d[v + 1] + MUL(xu, y[v + 1]) + r1; 51 r1 = z >> 32; 52 t = (uint32_t)z; 53 z = (uint64_t)t + MUL(f, m[v + 1]) + r2; 54 r2 = z >> 32; 55 if (v != 0) { 56 d[v] = (uint32_t)z; 57 } 58 } 59 zh = dh + r1 + r2; 60 d[len] = (uint32_t)zh; 61 dh = zh >> 32; 62 } 63 64 /* 65 * d[] may still be greater than m[] at that point; notably, the 66 * 'dh' word may be non-zero. 67 */ 68 br_i32_sub(d, m, NEQ(dh, 0) | NOT(br_i32_sub(d, m, 0))); 69 } 70