4f86c39515
* Update Dilithium * Alternative montgomery reduce to avoid i386 functest errors * Explicit casts for msvc * More casts; bump upstream version; fix metadata * another cast
70 lines
1.9 KiB
C
70 lines
1.9 KiB
C
#include "params.h"
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#include "reduce.h"
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#include <stdint.h>
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/*************************************************
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* Name: PQCLEAN_DILITHIUM3_CLEAN_montgomery_reduce
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*
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* Description: For finite field element a with -2^{31}Q <= a <= Q*2^31,
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* compute r \equiv a*2^{-32} (mod Q) such that -Q < r < Q.
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*
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* Arguments: - int64_t: finite field element a
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*
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* Returns r.
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**************************************************/
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int32_t PQCLEAN_DILITHIUM3_CLEAN_montgomery_reduce(int64_t a) {
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int32_t t;
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t = (int32_t)((uint64_t)a * (uint64_t)QINV);
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t = (a - (int64_t)t * Q) >> 32;
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return t;
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}
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/*************************************************
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* Name: PQCLEAN_DILITHIUM3_CLEAN_reduce32
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*
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* Description: For finite field element a with a <= 2^{31} - 2^{22} - 1,
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* compute r \equiv a (mod Q) such that -6283009 <= r <= 6283007.
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*
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* Arguments: - int32_t: finite field element a
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*
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* Returns r.
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**************************************************/
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int32_t PQCLEAN_DILITHIUM3_CLEAN_reduce32(int32_t a) {
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int32_t t;
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t = (a + (1 << 22)) >> 23;
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t = a - t * Q;
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return t;
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}
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/*************************************************
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* Name: PQCLEAN_DILITHIUM3_CLEAN_caddq
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*
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* Description: Add Q if input coefficient is negative.
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*
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* Arguments: - int32_t: finite field element a
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*
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* Returns r.
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**************************************************/
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int32_t PQCLEAN_DILITHIUM3_CLEAN_caddq(int32_t a) {
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a += (a >> 31) & Q;
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return a;
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}
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/*************************************************
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* Name: PQCLEAN_DILITHIUM3_CLEAN_freeze
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*
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* Description: For finite field element a, compute standard
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* representative r = a mod^+ Q.
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*
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* Arguments: - int32_t: finite field element a
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*
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* Returns r.
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**************************************************/
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int32_t PQCLEAN_DILITHIUM3_CLEAN_freeze(int32_t a) {
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a = PQCLEAN_DILITHIUM3_CLEAN_reduce32(a);
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a = PQCLEAN_DILITHIUM3_CLEAN_caddq(a);
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return a;
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}
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