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- /* Copyright (c) 2016, Google Inc.
- *
- * Permission to use, copy, modify, and/or distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
- * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
- * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
- * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
- * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
- * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
-
- #include "internal.h"
-
-
- /* Incomplete-reduction routines; for details on allowed input ranges
- * and produced output ranges, see the description in the paper:
- * https://cryptojedi.org/papers/#newhope */
-
- static const uint32_t kQInv = 12287; /* -inverse_mod(p,2^18) */
- static const uint32_t kRLog = 18;
-
- uint16_t newhope_montgomery_reduce(uint32_t a) {
- uint32_t u;
-
- u = (a * kQInv);
- u &= ((1 << kRLog) - 1);
- u *= PARAM_Q;
- a = a + u;
- return a >> 18;
- }
-
- uint16_t newhope_barrett_reduce(uint16_t a) {
- uint32_t u;
-
- u = ((uint32_t)a * 5) >> 16;
- u *= PARAM_Q;
- a -= u;
- return a;
- }
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