d8f336564f
This commit adds a nonce function that will be used by default for ECDSA adaptor signatures. This nonce function is similar to secp256k1_nonce_function_hardened except it uses the compressed 33-byte encoding for the pubkey argument. We need 33 bytes instead of 32 because, unlike with BIP-340, an ECDSA X-coordinate alone is not sufficient to disambiguate the Y-coordinate.
54 lines
2.1 KiB
C
54 lines
2.1 KiB
C
#ifndef SECP256K1_ECDSA_ADAPTOR_H
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#define SECP256K1_ECDSA_ADAPTOR_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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/** This module implements single signer ECDSA adaptor signatures following
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* "One-Time Verifiably Encrypted Signatures A.K.A. Adaptor Signatures" by
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* Lloyd Fournier
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* (https://lists.linuxfoundation.org/pipermail/lightning-dev/2019-November/002316.html
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* and https://github.com/LLFourn/one-time-VES/blob/master/main.pdf).
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*/
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/** A pointer to a function to deterministically generate a nonce.
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*
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* Same as secp256k1_nonce_function_hardened with the exception of using the
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* compressed 33-byte encoding for the pubkey argument.
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*
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* Returns: 1 if a nonce was successfully generated. 0 will cause signing to
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* return an error.
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* Out: nonce32: pointer to a 32-byte array to be filled by the function
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* In: msg32: the 32-byte message hash being verified
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* key32: pointer to a 32-byte secret key
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* pk33: the 33-byte serialized pubkey corresponding to key32
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* algo: pointer to an array describing the signature algorithm
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* algolen: the length of the algo array
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* data: arbitrary data pointer that is passed through
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*
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* Except for test cases, this function should compute some cryptographic hash of
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* the message, the key, the pubkey, the algorithm description, and data.
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*/
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typedef int (*secp256k1_nonce_function_hardened_ecdsa_adaptor)(
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unsigned char *nonce32,
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const unsigned char *msg32,
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const unsigned char *key32,
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const unsigned char *pk33,
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const unsigned char *algo,
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size_t algolen,
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void *data
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);
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/** A modified BIP-340 nonce generation function. If a data pointer is passed, it is
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* assumed to be a pointer to 32 bytes of auxiliary random data as defined in BIP-340.
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* The hash will be tagged with algo after removing all terminating null bytes.
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*/
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SECP256K1_API extern const secp256k1_nonce_function_hardened_ecdsa_adaptor secp256k1_nonce_function_ecdsa_adaptor;
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#ifdef __cplusplus
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}
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#endif
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#endif /* SECP256K1_ECDSA_ADAPTOR_H */
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