92 lines
2.9 KiB
C
92 lines
2.9 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_RAINBOWVCIRCUMZENITHAL_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_RAINBOWVCIRCUMZENITHAL_CLEAN_gf256_is_nonzero(uint8_t a) {
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unsigned int a8 = a;
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unsigned int r = ((unsigned int)0) - a8;
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r >>= 8;
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return r & 1;
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}
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static inline uint8_t gf4_mul_3(uint8_t a) {
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uint8_t msk = (uint8_t)((a - 2) >> 1);
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return (uint8_t)((msk & ((int)a * 3)) | ((~msk) & ((int)a - 1)));
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}
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static inline uint8_t gf16_mul_8(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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return (uint8_t)((gf4_mul_2(a0 ^ a1) << 2) | gf4_mul_3(a1));
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}
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// gf256 := gf16[X]/X^2+X+xy
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uint8_t PQCLEAN_RAINBOWVCIRCUMZENITHAL_CLEAN_gf256_mul(uint8_t a, uint8_t b) {
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uint8_t a0 = a & 15;
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uint8_t a1 = (a >> 4);
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uint8_t b0 = b & 15;
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uint8_t b1 = (b >> 4);
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uint8_t a0b0 = PQCLEAN_RAINBOWVCIRCUMZENITHAL_CLEAN_gf16_mul(a0, b0);
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uint8_t a1b1 = PQCLEAN_RAINBOWVCIRCUMZENITHAL_CLEAN_gf16_mul(a1, b1);
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uint8_t a0b1_a1b0 = PQCLEAN_RAINBOWVCIRCUMZENITHAL_CLEAN_gf16_mul(a0 ^ a1, b0 ^ b1) ^ a0b0 ^ a1b1;
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uint8_t a1b1_x8 = gf16_mul_8(a1b1);
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return (uint8_t)((a0b1_a1b0 ^ a1b1) << 4 ^ a0b0 ^ a1b1_x8);
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}
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static inline uint8_t gf256_squ(uint8_t a) {
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uint8_t a0 = a & 15;
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uint8_t a1 = (a >> 4);
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a1 = gf16_squ(a1);
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uint8_t a1squ_x8 = gf16_mul_8(a1);
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return (uint8_t)((a1 << 4) ^ a1squ_x8 ^ gf16_squ(a0));
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}
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uint8_t PQCLEAN_RAINBOWVCIRCUMZENITHAL_CLEAN_gf256_inv(uint8_t a) {
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// 128+64+32+16+8+4+2 = 254
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uint8_t a2 = gf256_squ(a);
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uint8_t a4 = gf256_squ(a2);
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uint8_t a8 = gf256_squ(a4);
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uint8_t a4_2 = PQCLEAN_RAINBOWVCIRCUMZENITHAL_CLEAN_gf256_mul(a4, a2);
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uint8_t a8_4_2 = PQCLEAN_RAINBOWVCIRCUMZENITHAL_CLEAN_gf256_mul(a4_2, a8);
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uint8_t a64_ = gf256_squ(a8_4_2);
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a64_ = gf256_squ(a64_);
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a64_ = gf256_squ(a64_);
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uint8_t a64_2 = PQCLEAN_RAINBOWVCIRCUMZENITHAL_CLEAN_gf256_mul(a64_, a8_4_2);
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uint8_t a128_ = gf256_squ(a64_2);
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return PQCLEAN_RAINBOWVCIRCUMZENITHAL_CLEAN_gf256_mul(a2, a128_);
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}
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