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 *  Args:          ctx: pointer to a context object
 *  Out:       session: pointer to a struct to store the session
 *  In:       aggnonce: pointer to an aggregate public nonce object that is the
 *                      output of musig_nonce_agg
 *              msg32:  the 32-byte message to sign
 *       keyagg_cache:  pointer to the keyagg_cache that was used to create the
 *                      aggregate (and potentially tweaked) pubkey
 */
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_musig_nonce_process(
    const secp256k1_context *ctx,
    secp256k1_musig_session *session,
    const secp256k1_musig_aggnonce *aggnonce,
    const unsigned char *msg32,
    const secp256k1_musig_keyagg_cache *keyagg_cache
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5);

/** Produces a partial signature
 *
 *  This function overwrites the given secnonce with zeros and will abort if given a
 *  secnonce that is all zeros. This is a best effort attempt to protect against nonce
 *  reuse. However, this is of course easily defeated if the secnonce has been
 *  copied (or serialized). Remember that nonce reuse will leak the secret key!
 *
 *  For signing to succeed, the secnonce provided to this function must have
 *  been generated for the provided keypair. This means that when signing for a
 *  keypair consisting of a seckey and pubkey, the secnonce must have been
 *  created by calling musig_nonce_gen with that pubkey. Otherwise, the
 *  illegal_callback is called.
 *
 *  This function does not verify the output partial signature, deviating from
 *  the BIP 327 specification. It is recommended to verify the output partial
 *  signature with `secp256k1_musig_partial_sig_verify` to prevent random or
 *  adversarially provoked computation errors.
 *
 *  Returns: 0 if the arguments are invalid or the provided secnonce has already
 *           been used for signing, 1 otherwise
 *  Args:         ctx: pointer to a context object
 *  Out:  partial_sig: pointer to struct to store the partial signature
 *  In/Out:  secnonce: pointer to the secnonce struct created in
 *                     musig_nonce_gen that has been never used in a
 *                     partial_sign call before and has been created for the
 *                     keypair
 *  In:       keypair: pointer to keypair to sign the message with
 *       keyagg_cache: pointer to the keyagg_cache that was output when the
 *                     aggregate public key for this session
 *            session: pointer to the session that was created with
 *                     musig_nonce_process
 */
SECP256K1_API int secp256k1_musig_partial_sign(
    const secp256k1_context *ctx,
    secp256k1_musig_partial_sig *partial_sig,
    secp256k1_musig_secnonce *secnonce,
    const secp256k1_keypair *keypair,
    const secp256k1_musig_keyagg_cache *keyagg_cache,
    const secp256k1_musig_session *session
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5) SECP256K1_ARG_NONNULL(6);

/** Verifies an individual signer's partial signature
 *
 *  The signature is verified for a specific signing session. In order to avoid
 *  accidentally verifying a signature from a different or non-existing signing
 *  session, you must ensure the following:
 *    1. The `keyagg_cache` argument is identical to the one used to create the
 *       `session` with `musig_nonce_process`.
 *    2. The `pubkey` argument must be identical to the one sent by the signer
 *       before aggregating it with `musig_pubkey_agg` to create the
 *       `keyagg_cache`.
 *    3. The `pubnonce` argument must be identical to the one sent by the signer
 *       before aggregating it with `musig_nonce_agg` and using the result to
 *       create the `session` with `musig_nonce_process`.
 *
 *  It is not required to call this function in regular MuSig sessions, because
 *  if any partial signature does not verify, the final signature will not
 *  verify either, so the problem will be caught. However, this function
 *  provides the ability to identify which specific partial signature fails
 *  verification.
 *
 *  Returns: 0 if the arguments are invalid or the partial signature does not
 *           verify, 1 otherwise
 *  Args         ctx: pointer to a context object
 *  In:  partial_sig: pointer to partial signature to verify, sent by
 *                    the signer associated with `pubnonce` and `pubkey`
 *          pubnonce: public nonce of the signer in the signing session
 *            pubkey: public key of the signer in the signing session
 *      keyagg_cache: pointer to the keyagg_cache that was output when the
 *                    aggregate public key for this signing session
 *           session: pointer to the session that was created with
 *                    `musig_nonce_process`
 */
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_musig_partial_sig_verify(
    const secp256k1_context *ctx,
    const secp256k1_musig_partial_sig *partial_sig,
    const secp256k1_musig_pubnonce *pubnonce,
    const secp256k1_pubkey *pubkey,
    const secp256k1_musig_keyagg_cache *keyagg_cache,
    const secp256k1_musig_session *session
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5) SECP256K1_ARG_NONNULL(6);

/** Aggregates partial signatures
 *
 *  Returns: 0 if the arguments are invalid, 1 otherwise (which does NOT mean
 *           the resulting signature verifies).
 *  Args:         ctx: pointer to a context object
 *  Out:        sig64: complete (but possibly invalid) Schnorr signature
 *  In:       session: pointer to the session that was created with
 *                     musig_nonce_process
 *       partial_sigs: array of pointers to partial signatures to aggregate
 *             n_sigs: number of elements in the partial_sigs array. Must be
 *                     greater than 0.
 */
SECP256K1_API int secp256k1_musig_partial_sig_agg(
    const secp256k1_context *ctx,
    unsigned char *sig64,
    const secp256k1_musig_session *session,
    const secp256k1_musig_partial_sig * const *partial_sigs,
    size_t n_sigs
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);

#ifdef __cplusplus
}
#endif