pqcrypto/crypto_kem/kyber768/clean/symmetric-fips202.c

#include "fips202.h"
#include "symmetric.h"

#include <stdlib.h>

/*************************************************
* Name:        PQCLEAN_KYBER768_CLEAN_kyber_shake128_absorb
*
* Description: Absorb step of the SHAKE128 specialized for the Kyber context.
*
* Arguments:   - shake128ctx *s:                  pointer to (uninitialized) output Keccak state
*              - const unsigned char *input:      pointer to KYBER_SYMBYTES input to be absorbed into s
*              - unsigned char i                  additional byte of input
*              - unsigned char j                  additional byte of input
**************************************************/
void PQCLEAN_KYBER768_CLEAN_kyber_shake128_absorb(shake128ctx *s, const unsigned char *input, unsigned char x, unsigned char y) {
    unsigned char extseed[KYBER_SYMBYTES + 2];
    int i;

    for (i = 0; i < KYBER_SYMBYTES; i++) {
        extseed[i] = input[i];
    }
    extseed[i++] = x;
    extseed[i]   = y;
    shake128_absorb(s, extseed, KYBER_SYMBYTES + 2);
}

/*************************************************
* Name:        PQCLEAN_KYBER768_CLEAN_kyber_shake128_squeezeblocks
*
* Description: Squeeze step of SHAKE128 XOF. Squeezes full blocks of SHAKE128_RATE bytes each.
*              Modifies the state. Can be called multiple times to keep squeezing,
*              i.e., is incremental.
*
* Arguments:   - unsigned char *output:      pointer to output blocks
*              - size_t nblocks:             number of blocks to be squeezed (written to output)
*              - shake128ctx *s:             pointer to in/output Keccak state
**************************************************/
void PQCLEAN_KYBER768_CLEAN_kyber_shake128_squeezeblocks(unsigned char *output, size_t nblocks, shake128ctx *s) {
    shake128_squeezeblocks(output, nblocks, s);
}

/*************************************************
* Name:        PQCLEAN_KYBER768_CLEAN_shake256_prf
*
* Description: Usage of SHAKE256 as a PRF, concatenates secret and public input
*              and then generates outlen bytes of SHAKE256 output
*
* Arguments:   - unsigned char *output:      pointer to output
*              - size_t outlen:              number of requested output bytes
*              - const unsigned char * key:  pointer to the key (of length KYBER_SYMBYTES)
*              - const unsigned char nonce:  single-byte nonce (public PRF input)
**************************************************/
void PQCLEAN_KYBER768_CLEAN_shake256_prf(unsigned char *output, size_t outlen, const unsigned char *key, unsigned char nonce) {
    unsigned char extkey[KYBER_SYMBYTES + 1];
    size_t i;

    for (i = 0; i < KYBER_SYMBYTES; i++) {
        extkey[i] = key[i];
    }
    extkey[i] = nonce;

    shake256(output, outlen, extkey, KYBER_SYMBYTES + 1);
}