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_from_monty(uint32_t *x, const uint32_t *m, uint32_t m0i) 30 { 31 size_t len, u, v; 32 33 len = (m[0] + 31) >> 5; 34 for (u = 0; u < len; u ++) { 35 uint32_t f; 36 uint64_t cc; 37 38 f = x[1] * m0i; 39 cc = 0; 40 for (v = 0; v < len; v ++) { 41 uint64_t z; 42 43 z = (uint64_t)x[v + 1] + MUL(f, m[v + 1]) + cc; 44 cc = z >> 32; 45 if (v != 0) { 46 x[v] = (uint32_t)z; 47 } 48 } 49 x[len] = (uint32_t)cc; 50 } 51 52 /* 53 * We may have to do an extra subtraction, but only if the 54 * value in x[] is indeed greater than or equal to that of m[], 55 * which is why we must do two calls (first call computes the 56 * carry, second call performs the subtraction only if the carry 57 * is 0). 58 */ 59 br_i32_sub(x, m, NOT(br_i32_sub(x, m, 0))); 60 } 61