mirror of
https://github.com/henrydcase/pqc.git
synced 2024-11-30 03:11:43 +00:00
64 lines
1.8 KiB
C
64 lines
1.8 KiB
C
#include "gf.h"
|
|
#include "parameters.h"
|
|
#include <stdint.h>
|
|
/**
|
|
* @file gf.c
|
|
* Galois field implementation with multiplication using lookup tables
|
|
*/
|
|
|
|
|
|
/**
|
|
* @brief Multiplies nonzero element a by element b
|
|
* @returns the product a*b
|
|
* @param[in] a First element of GF(2^PARAM_M) to multiply (cannot be zero)
|
|
* @param[in] b Second element of GF(2^PARAM_M) to multiply (cannot be zero)
|
|
*/
|
|
uint16_t PQCLEAN_HQCRMRS256_CLEAN_gf_mul(uint16_t a, uint16_t b) {
|
|
uint16_t mask;
|
|
mask = (uint16_t) (-((int32_t) a) >> 31); // a != 0
|
|
mask &= (uint16_t) (-((int32_t) b) >> 31); // b != 0
|
|
return mask & gf_exp[PQCLEAN_HQCRMRS256_CLEAN_gf_mod(gf_log[a] + gf_log[b])];
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
* @brief Squares an element of GF(2^PARAM_M)
|
|
* @returns a^2
|
|
* @param[in] a Element of GF(2^PARAM_M)
|
|
*/
|
|
uint16_t PQCLEAN_HQCRMRS256_CLEAN_gf_square(uint16_t a) {
|
|
int16_t mask = (uint16_t) (-((int32_t) a) >> 31); // a != 0
|
|
return mask & gf_exp[PQCLEAN_HQCRMRS256_CLEAN_gf_mod(2 * gf_log[a])];
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
* @brief Computes the inverse of an element of GF(2^PARAM_M)
|
|
* @returns the inverse of a
|
|
* @param[in] a Element of GF(2^PARAM_M)
|
|
*/
|
|
uint16_t PQCLEAN_HQCRMRS256_CLEAN_gf_inverse(uint16_t a) {
|
|
int16_t mask = (uint16_t) (-((int32_t) a) >> 31); // a != 0
|
|
return mask & gf_exp[PARAM_GF_MUL_ORDER - gf_log[a]];
|
|
}
|
|
|
|
|
|
|
|
/**
|
|
* @brief Returns i modulo 2^PARAM_M-1
|
|
* i must be less than 2*(2^PARAM_M-1).
|
|
* Therefore, the return value is either i or i-2^PARAM_M+1.
|
|
* @returns i mod (2^PARAM_M-1)
|
|
* @param[in] i The integer whose modulo is taken
|
|
*/
|
|
uint16_t PQCLEAN_HQCRMRS256_CLEAN_gf_mod(uint16_t i) {
|
|
uint16_t tmp = (uint16_t) (i - PARAM_GF_MUL_ORDER);
|
|
|
|
// mask = 0xffff if(i < PARAM_GF_MUL_ORDER)
|
|
uint16_t mask = -(tmp >> 15);
|
|
|
|
return tmp + (mask & PARAM_GF_MUL_ORDER);
|
|
}
|