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pqclean/crypto_sign/falcon-512/avx2/inner.h  view on Meta::CPAN

/* ==================================================================== */
/*
 * Support functions used for both signature generation and signature
 * verification (common.c).
 */

/*
 * From a SHAKE256 context (must be already flipped), produce a new
 * point. This is the non-constant-time version, which may leak enough
 * information to serve as a stop condition on a brute force attack on
 * the hashed message (provided that the nonce value is known).
 */
void PQCLEAN_FALCON512_AVX2_hash_to_point_vartime(inner_shake256_context *sc,
        uint16_t *x, unsigned logn);

/*
 * From a SHAKE256 context (must be already flipped), produce a new
 * point. The temporary buffer (tmp) must have room for 2*2^logn bytes.
 * This function is constant-time but is typically more expensive than
 * PQCLEAN_FALCON512_AVX2_hash_to_point_vartime().
 *
 * tmp[] must have 16-bit alignment.
 */
void PQCLEAN_FALCON512_AVX2_hash_to_point_ct(inner_shake256_context *sc,
        uint16_t *x, unsigned logn, uint8_t *tmp);

/*
 * Tell whether a given vector (2N coordinates, in two halves) is
 * acceptable as a signature. This compares the appropriate norm of the
 * vector with the acceptance bound. Returned value is 1 on success
 * (vector is short enough to be acceptable), 0 otherwise.
 */
int PQCLEAN_FALCON512_AVX2_is_short(const int16_t *s1, const int16_t *s2, unsigned logn);

/*
 * Tell whether a given vector (2N coordinates, in two halves) is
 * acceptable as a signature. Instead of the first half s1, this
 * function receives the "saturated squared norm" of s1, i.e. the
 * sum of the squares of the coordinates of s1 (saturated at 2^32-1
 * if the sum exceeds 2^31-1).
 *
 * Returned value is 1 on success (vector is short enough to be
 * acceptable), 0 otherwise.
 */
int PQCLEAN_FALCON512_AVX2_is_short_half(uint32_t sqn, const int16_t *s2, unsigned logn);

/* ==================================================================== */
/*
 * Signature verification functions (vrfy.c).
 */

/*
 * Convert a public key to NTT + Montgomery format. Conversion is done
 * in place.
 */
void PQCLEAN_FALCON512_AVX2_to_ntt_monty(uint16_t *h, unsigned logn);

/*
 * Internal signature verification code:
 *   c0[]      contains the hashed nonce+message
 *   s2[]      is the decoded signature
 *   h[]       contains the public key, in NTT + Montgomery format
 *   logn      is the degree log
 *   tmp[]     temporary, must have at least 2*2^logn bytes
 * Returned value is 1 on success, 0 on error.
 *
 * tmp[] must have 16-bit alignment.
 */
int PQCLEAN_FALCON512_AVX2_verify_raw(const uint16_t *c0, const int16_t *s2,
                                      const uint16_t *h, unsigned logn, uint8_t *tmp);

/*
 * Compute the public key h[], given the private key elements f[] and
 * g[]. This computes h = g/f mod phi mod q, where phi is the polynomial
 * modulus. This function returns 1 on success, 0 on error (an error is
 * reported if f is not invertible mod phi mod q).
 *
 * The tmp[] array must have room for at least 2*2^logn elements.
 * tmp[] must have 16-bit alignment.
 */
int PQCLEAN_FALCON512_AVX2_compute_public(uint16_t *h,
        const int8_t *f, const int8_t *g, unsigned logn, uint8_t *tmp);

/*
 * Recompute the fourth private key element. Private key consists in
 * four polynomials with small coefficients f, g, F and G, which are
 * such that fG - gF = q mod phi; furthermore, f is invertible modulo
 * phi and modulo q. This function recomputes G from f, g and F.
 *
 * The tmp[] array must have room for at least 4*2^logn bytes.
 *
 * Returned value is 1 in success, 0 on error (f not invertible).
 * tmp[] must have 16-bit alignment.
 */
int PQCLEAN_FALCON512_AVX2_complete_private(int8_t *G,
        const int8_t *f, const int8_t *g, const int8_t *F,
        unsigned logn, uint8_t *tmp);

/*
 * Test whether a given polynomial is invertible modulo phi and q.
 * Polynomial coefficients are small integers.
 *
 * tmp[] must have 16-bit alignment.
 */
int PQCLEAN_FALCON512_AVX2_is_invertible(
    const int16_t *s2, unsigned logn, uint8_t *tmp);

/*
 * Count the number of elements of value zero in the NTT representation
 * of the given polynomial: this is the number of primitive 2n-th roots
 * of unity (modulo q = 12289) that are roots of the provided polynomial
 * (taken modulo q).
 *
 * tmp[] must have 16-bit alignment.
 */
int PQCLEAN_FALCON512_AVX2_count_nttzero(const int16_t *sig, unsigned logn, uint8_t *tmp);

/*
 * Internal signature verification with public key recovery:
 *   h[]       receives the public key (NOT in NTT/Montgomery format)
 *   c0[]      contains the hashed nonce+message