74 lines
2.3 KiB
C
74 lines
2.3 KiB
C
#include "verify.h"
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#include <immintrin.h>
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#include <stdint.h>
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#include <stdlib.h>
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/*************************************************
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* Name: PQCLEAN_KYBER51290S_AVX2_verify
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*
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* Description: Compare two arrays for equality in constant time.
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*
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* Arguments: const uint8_t *a: pointer to first byte array
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* const uint8_t *b: pointer to second byte array
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* size_t len: length of the byte arrays
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*
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* Returns 0 if the byte arrays are equal, 1 otherwise
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**************************************************/
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int PQCLEAN_KYBER51290S_AVX2_verify(const uint8_t *a, const uint8_t *b, size_t len) {
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size_t i;
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uint64_t r;
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__m256i f, g, h;
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h = _mm256_setzero_si256();
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for (i = 0; i < len / 32; i++) {
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f = _mm256_loadu_si256((__m256i *)&a[32 * i]);
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g = _mm256_loadu_si256((__m256i *)&b[32 * i]);
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f = _mm256_xor_si256(f, g);
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h = _mm256_or_si256(h, f);
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}
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r = 1 - _mm256_testz_si256(h, h);
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a += 32 * i;
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b += 32 * i;
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len -= 32 * i;
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for (i = 0; i < len; i++) {
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r |= a[i] ^ b[i];
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}
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r = (-r) >> 63;
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return r;
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}
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/*************************************************
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* Name: PQCLEAN_KYBER51290S_AVX2_cmov
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*
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* Description: Copy len bytes from x to r if b is 1;
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* don't modify x if b is 0. Requires b to be in {0,1};
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* assumes two's complement representation of negative integers.
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* Runs in constant time.
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*
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* Arguments: unsigned char *r: pointer to output byte array
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* const unsigned char *x: pointer to input byte array
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* size_t len: Amount of bytes to be copied
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* unsigned char b: Condition bit; has to be in {0,1}
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**************************************************/
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void PQCLEAN_KYBER51290S_AVX2_cmov(uint8_t *restrict r, const uint8_t *x, size_t len, uint8_t b) {
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size_t i;
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__m256i xvec, rvec, bvec;
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bvec = _mm256_set1_epi64x(-(uint64_t)b);
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for (i = 0; i < len / 32; i++) {
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rvec = _mm256_loadu_si256((__m256i *)&r[32 * i]);
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xvec = _mm256_loadu_si256((__m256i *)&x[32 * i]);
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rvec = _mm256_blendv_epi8(rvec, xvec, bvec);
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_mm256_storeu_si256((__m256i *)&r[32 * i], rvec);
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}
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r += 32 * i;
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x += 32 * i;
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len -= 32 * i;
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for (i = 0; i < len; i++) {
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r[i] ^= -b & (x[i] ^ r[i]);
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}
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}
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