55 lines
1.5 KiB
C
55 lines
1.5 KiB
C
#include "gf.h"
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//// gf4 := gf2[x]/x^2+x+1
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static inline uint8_t gf4_mul_2(uint8_t a) {
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uint8_t r = (uint8_t)(a << 1);
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r ^= (uint8_t)((a >> 1) * 7);
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return r;
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}
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static inline uint8_t gf4_mul(uint8_t a, uint8_t b) {
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uint8_t r = (uint8_t)(a * (b & 1));
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return r ^ (uint8_t)(gf4_mul_2(a) * (b >> 1));
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}
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static inline uint8_t gf4_squ(uint8_t a) {
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return a ^ (a >> 1);
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}
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//// gf16 := gf4[y]/y^2+y+x
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uint8_t PQCLEAN_RAINBOWICLASSIC_CLEAN_gf16_mul(uint8_t a, uint8_t b) {
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uint8_t a0 = a & 3;
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uint8_t a1 = (a >> 2);
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uint8_t b0 = b & 3;
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uint8_t b1 = (b >> 2);
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uint8_t a0b0 = gf4_mul(a0, b0);
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uint8_t a1b1 = gf4_mul(a1, b1);
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uint8_t a0b1_a1b0 = gf4_mul(a0 ^ a1, b0 ^ b1) ^ a0b0 ^ a1b1;
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uint8_t a1b1_x2 = gf4_mul_2(a1b1);
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return (uint8_t)((a0b1_a1b0 ^ a1b1) << 2 ^ a0b0 ^ a1b1_x2);
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}
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static inline uint8_t gf16_squ(uint8_t a) {
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uint8_t a0 = a & 3;
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uint8_t a1 = (a >> 2);
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a1 = gf4_squ(a1);
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uint8_t a1squ_x2 = gf4_mul_2(a1);
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return (uint8_t)((a1 << 2) ^ a1squ_x2 ^ gf4_squ(a0));
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}
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uint8_t PQCLEAN_RAINBOWICLASSIC_CLEAN_gf16_is_nonzero(uint8_t a) {
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unsigned int a4 = a & 0xf;
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unsigned int r = ((unsigned int)0) - a4;
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r >>= 4;
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return r & 1;
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}
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uint8_t PQCLEAN_RAINBOWICLASSIC_CLEAN_gf16_inv(uint8_t a) {
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uint8_t a2 = gf16_squ(a);
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uint8_t a4 = gf16_squ(a2);
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uint8_t a8 = gf16_squ(a4);
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uint8_t a6 = PQCLEAN_RAINBOWICLASSIC_CLEAN_gf16_mul(a4, a2);
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return PQCLEAN_RAINBOWICLASSIC_CLEAN_gf16_mul(a8, a6);
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}
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