76 lines
2.6 KiB
C
76 lines
2.6 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_KYBER768_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 unsigned char *a: pointer to first byte array
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* const unsigned char *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_KYBER768_AVX2_verify(const uint8_t *a, const uint8_t *b, size_t len) {
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size_t pos = 0;
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uint64_t r = 0;
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__m256i avec, bvec, cvec;
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cvec = _mm256_setzero_si256();
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for (pos = 0; pos + 32 <= len; pos += 32) {
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avec = _mm256_loadu_si256((__m256i *)&a[pos]);
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bvec = _mm256_loadu_si256((__m256i *)&b[pos]);
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avec = _mm256_xor_si256(avec, bvec);
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cvec = _mm256_or_si256(cvec, avec);
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}
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r = !_mm256_testz_si256(cvec, cvec);
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if (pos < len) {
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avec = _mm256_loadu_si256((__m256i *)&a[pos]);
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bvec = _mm256_loadu_si256((__m256i *)&b[pos]);
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cvec = _mm256_cmpeq_epi8(avec, bvec);
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r |= _mm256_movemask_epi8(cvec) & (-(uint32_t)1 >> (32 + pos - len));
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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_KYBER768_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_KYBER768_AVX2_cmov(uint8_t *restrict r, const uint8_t *restrict x, size_t len, uint8_t b) {
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size_t pos = 0;
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__m256i xvec, rvec, bvec;
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b = -b;
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bvec = _mm256_set1_epi8(b);
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for (pos = 0; pos + 32 <= len; pos += 32) {
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rvec = _mm256_loadu_si256((__m256i *)&r[pos]);
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xvec = _mm256_loadu_si256((__m256i *)&x[pos]);
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xvec = _mm256_xor_si256(xvec, rvec);
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xvec = _mm256_and_si256(xvec, bvec);
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rvec = _mm256_xor_si256(rvec, xvec);
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_mm256_storeu_si256((__m256i *)&r[pos], rvec);
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}
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while (pos < len) {
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r[pos] ^= b & (x[pos] ^ r[pos]);
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pos += 1;
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}
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}
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