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#ifndef _SECP256K1_SCHNORR_
# define _SECP256K1_SCHNORR_
# include "secp256k1.h"
# ifdef __cplusplus
extern "C" {
# endif
/** Create a signature using a custom EC-Schnorr-SHA256 construction. It
* produces non-malleable 64-byte signatures which support public key recovery
* batch validation, and multiparty signing.
* Returns: 1: signature created
* 0: the nonce generation function failed, or the private key was
* invalid.
* Args: ctx: pointer to a context object, initialized for signing
* (cannot be NULL)
* Out: sig64: pointer to a 64-byte array where the signature will be
* placed (cannot be NULL)
* In: msg32: the 32-byte message hash being signed (cannot be NULL)
* seckey: pointer to a 32-byte secret key (cannot be NULL)
* noncefp:pointer to a nonce generation function. If NULL,
* secp256k1_nonce_function_default is used
* ndata: pointer to arbitrary data used by the nonce generation
* function (can be NULL)
*/
SECP256K1_API int secp256k1_schnorr_sign(
const secp256k1_context* ctx,
unsigned char *sig64,
const unsigned char *msg32,
const unsigned char *seckey,
secp256k1_nonce_function noncefp,
const void *ndata
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
/** Verify a signature created by secp256k1_schnorr_sign.
* Returns: 1: correct signature
* 0: incorrect signature
* Args: ctx: a secp256k1 context object, initialized for verification.
* In: sig64: the 64-byte signature being verified (cannot be NULL)
* msg32: the 32-byte message hash being verified (cannot be NULL)
* pubkey: the public key to verify with (cannot be NULL)
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_schnorr_verify(
const secp256k1_context* ctx,
const unsigned char *sig64,
const unsigned char *msg32,
const secp256k1_pubkey *pubkey
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
/** Recover an EC public key from a Schnorr signature created using
* secp256k1_schnorr_sign.
* Returns: 1: public key successfully recovered (which guarantees a correct
* signature).
* 0: otherwise.
* Args: ctx: pointer to a context object, initialized for
* verification (cannot be NULL)
* Out: pubkey: pointer to a pubkey to set to the recovered public key
* (cannot be NULL).
* In: sig64: signature as 64 byte array (cannot be NULL)
* msg32: the 32-byte message hash assumed to be signed (cannot
* be NULL)
*/
SECP256K1_API int secp256k1_schnorr_recover(
const secp256k1_context* ctx,
secp256k1_pubkey *pubkey,
const unsigned char *sig64,
const unsigned char *msg32
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
/** Generate a nonce pair deterministically for use with
* secp256k1_schnorr_partial_sign.
* Returns: 1: valid nonce pair was generated.
* 0: otherwise (nonce generation function failed)
* Args: ctx: pointer to a context object, initialized for signing
* (cannot be NULL)
* Out: pubnonce: public side of the nonce (cannot be NULL)
* privnonce32: private side of the nonce (32 byte) (cannot be NULL)
* In: msg32: the 32-byte message hash assumed to be signed (cannot
* be NULL)
* sec32: the 32-byte private key (cannot be NULL)
* noncefp: pointer to a nonce generation function. If NULL,
* secp256k1_nonce_function_default is used
* noncedata: pointer to arbitrary data used by the nonce generation
* function (can be NULL)
*
* Do not use the output as a private/public key pair for signing/validation.
*/
SECP256K1_API int secp256k1_schnorr_generate_nonce_pair(
const secp256k1_context* ctx,
secp256k1_pubkey *pubnonce,
unsigned char *privnonce32,
const unsigned char *msg32,
const unsigned char *sec32,
secp256k1_nonce_function noncefp,
const void* noncedata
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
/** Produce a partial Schnorr signature, which can be combined using
* secp256k1_schnorr_partial_combine, to end up with a full signature that is
* verifiable using secp256k1_schnorr_verify.
* Returns: 1: signature created successfully.
* 0: no valid signature exists with this combination of keys, nonces
* and message (chance around 1 in 2^128)
* -1: invalid private key, nonce, or public nonces.
* Args: ctx: pointer to context object, initialized for signing (cannot
* be NULL)
* Out: sig64: pointer to 64-byte array to put partial signature in
* In: msg32: pointer to 32-byte message to sign
* sec32: pointer to 32-byte private key
* pubnonce_others: pointer to pubkey containing the sum of the other's
* nonces (see secp256k1_ec_pubkey_combine)
* secnonce32: pointer to 32-byte array containing our nonce
*
* The intended procedure for creating a multiparty signature is:
* - Each signer S[i] with private key x[i] and public key Q[i] runs
* secp256k1_schnorr_generate_nonce_pair to produce a pair (k[i],R[i]) of
* private/public nonces.
* - All signers communicate their public nonces to each other (revealing your
* private nonce can lead to discovery of your private key, so it should be
* considered secret).
* - All signers combine all the public nonces they received (excluding their
* own) using secp256k1_ec_pubkey_combine to obtain an
* Rall[i] = sum(R[0..i-1,i+1..n]).
* - All signers produce a partial signature using
* secp256k1_schnorr_partial_sign, passing in their own private key x[i],
* their own private nonce k[i], and the sum of the others' public nonces
* Rall[i].
* - All signers communicate their partial signatures to each other.
* - Someone combines all partial signatures using
* secp256k1_schnorr_partial_combine, to obtain a full signature.
* - The resulting signature is validatable using secp256k1_schnorr_verify, with
* public key equal to the result of secp256k1_ec_pubkey_combine of the
* signers' public keys (sum(Q[0..n])).
*
* Note that secp256k1_schnorr_partial_combine and secp256k1_ec_pubkey_combine
* function take their arguments in any order, and it is possible to
* pre-combine several inputs already with one call, and add more inputs later
* by calling the function again (they are commutative and associative).
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_schnorr_partial_sign(
const secp256k1_context* ctx,
unsigned char *sig64,
const unsigned char *msg32,
const unsigned char *sec32,
const secp256k1_pubkey *pubnonce_others,
const unsigned char *secnonce32
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5) SECP256K1_ARG_NONNULL(6);
/** Combine multiple Schnorr partial signatures.
* Returns: 1: the passed signatures were successfully combined.
* 0: the resulting signature is not valid (chance of 1 in 2^256)
* -1: some inputs were invalid, or the signatures were not created
* using the same set of nonces
* Args: ctx: pointer to a context object
* Out: sig64: pointer to a 64-byte array to place the combined signature
* (cannot be NULL)
* In: sig64sin: pointer to an array of n pointers to 64-byte input
* signatures
* n: the number of signatures to combine (at least 1)
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_schnorr_partial_combine(
const secp256k1_context* ctx,
unsigned char *sig64,
const unsigned char * const * sig64sin,
size_t n
) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
# ifdef __cplusplus
}
# endif
#endif
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