diff options
Diffstat (limited to 'lib/liboqs/src/kem/kyber/pqcrystals-kyber_kyber768_ref/cbd.c')
-rw-r--r-- | lib/liboqs/src/kem/kyber/pqcrystals-kyber_kyber768_ref/cbd.c | 128 |
1 files changed, 128 insertions, 0 deletions
diff --git a/lib/liboqs/src/kem/kyber/pqcrystals-kyber_kyber768_ref/cbd.c b/lib/liboqs/src/kem/kyber/pqcrystals-kyber_kyber768_ref/cbd.c new file mode 100644 index 000000000..1500ffea5 --- /dev/null +++ b/lib/liboqs/src/kem/kyber/pqcrystals-kyber_kyber768_ref/cbd.c @@ -0,0 +1,128 @@ +#include <stdint.h> +#include "params.h" +#include "cbd.h" + +/************************************************* +* Name: load32_littleendian +* +* Description: load 4 bytes into a 32-bit integer +* in little-endian order +* +* Arguments: - const uint8_t *x: pointer to input byte array +* +* Returns 32-bit unsigned integer loaded from x +**************************************************/ +static uint32_t load32_littleendian(const uint8_t x[4]) +{ + uint32_t r; + r = (uint32_t)x[0]; + r |= (uint32_t)x[1] << 8; + r |= (uint32_t)x[2] << 16; + r |= (uint32_t)x[3] << 24; + return r; +} + +/************************************************* +* Name: load24_littleendian +* +* Description: load 3 bytes into a 32-bit integer +* in little-endian order. +* This function is only needed for Kyber-512 +* +* Arguments: - const uint8_t *x: pointer to input byte array +* +* Returns 32-bit unsigned integer loaded from x (most significant byte is zero) +**************************************************/ +#if KYBER_ETA1 == 3 +static uint32_t load24_littleendian(const uint8_t x[3]) +{ + uint32_t r; + r = (uint32_t)x[0]; + r |= (uint32_t)x[1] << 8; + r |= (uint32_t)x[2] << 16; + return r; +} +#endif + + +/************************************************* +* Name: cbd2 +* +* Description: Given an array of uniformly random bytes, compute +* polynomial with coefficients distributed according to +* a centered binomial distribution with parameter eta=2 +* +* Arguments: - poly *r: pointer to output polynomial +* - const uint8_t *buf: pointer to input byte array +**************************************************/ +static void cbd2(poly *r, const uint8_t buf[2*KYBER_N/4]) +{ + unsigned int i,j; + uint32_t t,d; + int16_t a,b; + + for(i=0;i<KYBER_N/8;i++) { + t = load32_littleendian(buf+4*i); + d = t & 0x55555555; + d += (t>>1) & 0x55555555; + + for(j=0;j<8;j++) { + a = (d >> (4*j+0)) & 0x3; + b = (d >> (4*j+2)) & 0x3; + r->coeffs[8*i+j] = a - b; + } + } +} + +/************************************************* +* Name: cbd3 +* +* Description: Given an array of uniformly random bytes, compute +* polynomial with coefficients distributed according to +* a centered binomial distribution with parameter eta=3. +* This function is only needed for Kyber-512 +* +* Arguments: - poly *r: pointer to output polynomial +* - const uint8_t *buf: pointer to input byte array +**************************************************/ +#if KYBER_ETA1 == 3 +static void cbd3(poly *r, const uint8_t buf[3*KYBER_N/4]) +{ + unsigned int i,j; + uint32_t t,d; + int16_t a,b; + + for(i=0;i<KYBER_N/4;i++) { + t = load24_littleendian(buf+3*i); + d = t & 0x00249249; + d += (t>>1) & 0x00249249; + d += (t>>2) & 0x00249249; + + for(j=0;j<4;j++) { + a = (d >> (6*j+0)) & 0x7; + b = (d >> (6*j+3)) & 0x7; + r->coeffs[4*i+j] = a - b; + } + } +} +#endif + +void poly_cbd_eta1(poly *r, const uint8_t buf[KYBER_ETA1*KYBER_N/4]) +{ +#if KYBER_ETA1 == 2 + cbd2(r, buf); +#elif KYBER_ETA1 == 3 + cbd3(r, buf); +#else +#error "This implementation requires eta1 in {2,3}" +#endif +} + +void poly_cbd_eta2(poly *r, const uint8_t buf[KYBER_ETA2*KYBER_N/4]) +{ +#if KYBER_ETA2 == 2 + cbd2(r, buf); +#else +#error "This implementation requires eta2 = 2" +#endif +} |