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pqcrypto/crypto_kem/sntrup653/clean/crypto_encode_653xfreeze3.c

26 lines
594 B
C

#include "crypto_encode_653xfreeze3.h"
#define int16 int16_t
#define p 653
/* valid inputs: -16384 <= x < 16384 */
/* then 3 divides x-F3_freeze(x) */
/* and F3_freeze(x) is in {-1,0,1} */
/* all inputs: 3 divides x-F3_freeze(x) */
/* and F3_freeze(x) is in {-2,-1,0,1,2} */
static inline unsigned char F3_freeze(int16 x) {
return (unsigned char) (x - 3 * ((10923 * x + 16384) >> 15));
}
void PQCLEAN_SNTRUP653_CLEAN_crypto_encode_653xfreeze3(unsigned char *s, const void *v) {
const int16 *r = v;
int i;
for (i = 0; i < p; ++i) {
s[i] = F3_freeze(r[i]);
}
}