diff options
Diffstat (limited to 'src/secp256k1/include/secp256k1_schnorrsig.h')
| -rw-r--r-- | src/secp256k1/include/secp256k1_schnorrsig.h | 115 |
1 files changed, 87 insertions, 28 deletions
diff --git a/src/secp256k1/include/secp256k1_schnorrsig.h b/src/secp256k1/include/secp256k1_schnorrsig.h index 0150cd3395..74cbcac45e 100644 --- a/src/secp256k1/include/secp256k1_schnorrsig.h +++ b/src/secp256k1/include/secp256k1_schnorrsig.h @@ -23,24 +23,29 @@ extern "C" { * * Returns: 1 if a nonce was successfully generated. 0 will cause signing to * return an error. - * Out: nonce32: pointer to a 32-byte array to be filled by the function. - * In: msg32: the 32-byte message hash being verified (will not be NULL) - * key32: pointer to a 32-byte secret key (will not be NULL) - * xonly_pk32: the 32-byte serialized xonly pubkey corresponding to key32 - * (will not be NULL) - * algo16: pointer to a 16-byte array describing the signature - * algorithm (will not be NULL). - * data: Arbitrary data pointer that is passed through. + * Out: nonce32: pointer to a 32-byte array to be filled by the function + * In: msg: the message being verified. Is NULL if and only if msglen + * is 0. + * msglen: the length of the message + * key32: pointer to a 32-byte secret key (will not be NULL) + * xonly_pk32: the 32-byte serialized xonly pubkey corresponding to key32 + * (will not be NULL) + * algo: pointer to an array describing the signature + * algorithm (will not be NULL) + * algolen: the length of the algo array + * data: arbitrary data pointer that is passed through * * Except for test cases, this function should compute some cryptographic hash of * the message, the key, the pubkey, the algorithm description, and data. */ typedef int (*secp256k1_nonce_function_hardened)( unsigned char *nonce32, - const unsigned char *msg32, + const unsigned char *msg, + size_t msglen, const unsigned char *key32, const unsigned char *xonly_pk32, - const unsigned char *algo16, + const unsigned char *algo, + size_t algolen, void *data ); @@ -50,59 +55,113 @@ typedef int (*secp256k1_nonce_function_hardened)( * * If a data pointer is passed, it is assumed to be a pointer to 32 bytes of * auxiliary random data as defined in BIP-340. If the data pointer is NULL, - * schnorrsig_sign does not produce BIP-340 compliant signatures. The algo16 - * argument must be non-NULL, otherwise the function will fail and return 0. - * The hash will be tagged with algo16 after removing all terminating null - * bytes. Therefore, to create BIP-340 compliant signatures, algo16 must be set - * to "BIP0340/nonce\0\0\0" + * the nonce derivation procedure follows BIP-340 by setting the auxiliary + * random data to zero. The algo argument must be non-NULL, otherwise the + * function will fail and return 0. The hash will be tagged with algo. + * Therefore, to create BIP-340 compliant signatures, algo must be set to + * "BIP0340/nonce" and algolen to 13. */ SECP256K1_API extern const secp256k1_nonce_function_hardened secp256k1_nonce_function_bip340; +/** Data structure that contains additional arguments for schnorrsig_sign_custom. + * + * A schnorrsig_extraparams structure object can be initialized correctly by + * setting it to SECP256K1_SCHNORRSIG_EXTRAPARAMS_INIT. + * + * Members: + * magic: set to SECP256K1_SCHNORRSIG_EXTRAPARAMS_MAGIC at initialization + * and has no other function than making sure the object is + * initialized. + * noncefp: pointer to a nonce generation function. If NULL, + * secp256k1_nonce_function_bip340 is used + * ndata: pointer to arbitrary data used by the nonce generation function + * (can be NULL). If it is non-NULL and + * secp256k1_nonce_function_bip340 is used, then ndata must be a + * pointer to 32-byte auxiliary randomness as per BIP-340. + */ +typedef struct { + unsigned char magic[4]; + secp256k1_nonce_function_hardened noncefp; + void* ndata; +} secp256k1_schnorrsig_extraparams; + +#define SECP256K1_SCHNORRSIG_EXTRAPARAMS_MAGIC { 0xda, 0x6f, 0xb3, 0x8c } +#define SECP256K1_SCHNORRSIG_EXTRAPARAMS_INIT {\ + SECP256K1_SCHNORRSIG_EXTRAPARAMS_MAGIC,\ + NULL,\ + NULL\ +} + /** Create a Schnorr signature. * * Does _not_ strictly follow BIP-340 because it does not verify the resulting * signature. Instead, you can manually use secp256k1_schnorrsig_verify and * abort if it fails. * - * Otherwise BIP-340 compliant if the noncefp argument is NULL or - * secp256k1_nonce_function_bip340 and the ndata argument is 32-byte auxiliary - * randomness. + * This function only signs 32-byte messages. If you have messages of a + * different size (or the same size but without a context-specific tag + * prefix), it is recommended to create a 32-byte message hash with + * secp256k1_tagged_sha256 and then sign the hash. Tagged hashing allows + * providing an context-specific tag for domain separation. This prevents + * signatures from being valid in multiple contexts by accident. * * Returns 1 on success, 0 on failure. * Args: ctx: pointer to a context object, initialized for signing (cannot be NULL) * Out: sig64: pointer to a 64-byte array to store the serialized signature (cannot be NULL) * In: msg32: the 32-byte message being signed (cannot be NULL) * keypair: pointer to an initialized keypair (cannot be NULL) - * noncefp: pointer to a nonce generation function. If NULL, secp256k1_nonce_function_bip340 is used - * ndata: pointer to arbitrary data used by the nonce generation - * function (can be NULL). If it is non-NULL and - * secp256k1_nonce_function_bip340 is used, then ndata must be a - * pointer to 32-byte auxiliary randomness as per BIP-340. + * aux_rand32: 32 bytes of fresh randomness. While recommended to provide + * this, it is only supplemental to security and can be NULL. See + * BIP-340 "Default Signing" for a full explanation of this + * argument and for guidance if randomness is expensive. */ SECP256K1_API int secp256k1_schnorrsig_sign( const secp256k1_context* ctx, unsigned char *sig64, const unsigned char *msg32, const secp256k1_keypair *keypair, - secp256k1_nonce_function_hardened noncefp, - void *ndata + unsigned char *aux_rand32 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); +/** Create a Schnorr signature with a more flexible API. + * + * Same arguments as secp256k1_schnorrsig_sign except that it allows signing + * variable length messages and accepts a pointer to an extraparams object that + * allows customizing signing by passing additional arguments. + * + * Creates the same signatures as schnorrsig_sign if msglen is 32 and the + * extraparams.ndata is the same as aux_rand32. + * + * In: msg: the message being signed. Can only be NULL if msglen is 0. + * msglen: length of the message + * extraparams: pointer to a extraparams object (can be NULL) + */ +SECP256K1_API int secp256k1_schnorrsig_sign_custom( + const secp256k1_context* ctx, + unsigned char *sig64, + const unsigned char *msg, + size_t msglen, + const secp256k1_keypair *keypair, + secp256k1_schnorrsig_extraparams *extraparams +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(5); + /** Verify a Schnorr signature. * * Returns: 1: correct signature * 0: incorrect signature * Args: ctx: a secp256k1 context object, initialized for verification. * In: sig64: pointer to the 64-byte signature to verify (cannot be NULL) - * msg32: the 32-byte message being verified (cannot be NULL) + * msg: the message being verified. Can only be NULL if msglen is 0. + * msglen: length of the message * pubkey: pointer to an x-only public key to verify with (cannot be NULL) */ SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_schnorrsig_verify( const secp256k1_context* ctx, const unsigned char *sig64, - const unsigned char *msg32, + const unsigned char *msg, + size_t msglen, const secp256k1_xonly_pubkey *pubkey -) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4); +) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(5); #ifdef __cplusplus } |