Alien-libsecp256k1
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libsecp256k1/include/secp256k1.h view on Meta::CPAN
* encoded numbers are out of range.
*
* After the call, sig will always be initialized. If parsing failed or the
* encoded numbers are out of range, signature verification with it is
* guaranteed to fail for every message and public key.
*/
SECP256K1_API int secp256k1_ecdsa_signature_parse_der(
const secp256k1_context *ctx,
secp256k1_ecdsa_signature *sig,
const unsigned char *input,
size_t inputlen
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
/** Serialize an ECDSA signature in DER format.
*
* Returns: 1 if enough space was available to serialize, 0 otherwise
* Args: ctx: pointer to a context object
* Out: output: pointer to an array to store the DER serialization
* In/Out: outputlen: pointer to a length integer. Initially, this integer
* should be set to the length of output. After the call
* it will be set to the length of the serialization (even
* if 0 was returned).
* In: sig: pointer to an initialized signature object
*/
SECP256K1_API int secp256k1_ecdsa_signature_serialize_der(
const secp256k1_context *ctx,
unsigned char *output,
size_t *outputlen,
const secp256k1_ecdsa_signature *sig
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
/** Serialize an ECDSA signature in compact (64 byte) format.
*
* Returns: 1
* Args: ctx: pointer to a context object
* Out: output64: pointer to a 64-byte array to store the compact serialization
* In: sig: pointer to an initialized signature object
*
* See secp256k1_ecdsa_signature_parse_compact for details about the encoding.
*/
SECP256K1_API int secp256k1_ecdsa_signature_serialize_compact(
const secp256k1_context *ctx,
unsigned char *output64,
const secp256k1_ecdsa_signature *sig
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
/** Verify an ECDSA signature.
*
* Returns: 1: correct signature
* 0: incorrect or unparseable signature
* Args: ctx: pointer to a context object
* In: sig: the signature being verified.
* msghash32: the 32-byte message hash being verified.
* The verifier must make sure to apply a cryptographic
* hash function to the message by itself and not accept an
* msghash32 value directly. Otherwise, it would be easy to
* create a "valid" signature without knowledge of the
* secret key. See also
* https://bitcoin.stackexchange.com/a/81116/35586 for more
* background on this topic.
* pubkey: pointer to an initialized public key to verify with.
*
* To avoid accepting malleable signatures, only ECDSA signatures in lower-S
* form are accepted.
*
* If you need to accept ECDSA signatures from sources that do not obey this
* rule, apply secp256k1_ecdsa_signature_normalize to the signature prior to
* verification, but be aware that doing so results in malleable signatures.
*
* For details, see the comments for that function.
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdsa_verify(
const secp256k1_context *ctx,
const secp256k1_ecdsa_signature *sig,
const unsigned char *msghash32,
const secp256k1_pubkey *pubkey
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
/** Convert a signature to a normalized lower-S form.
*
* Returns: 1 if sigin was not normalized, 0 if it already was.
* Args: ctx: pointer to a context object
* Out: sigout: pointer to a signature to fill with the normalized form,
* or copy if the input was already normalized. (can be NULL if
* you're only interested in whether the input was already
* normalized).
* In: sigin: pointer to a signature to check/normalize (can be identical to sigout)
*
* With ECDSA a third-party can forge a second distinct signature of the same
* message, given a single initial signature, but without knowing the key. This
* is done by negating the S value modulo the order of the curve, 'flipping'
* the sign of the random point R which is not included in the signature.
*
* Forgery of the same message isn't universally problematic, but in systems
* where message malleability or uniqueness of signatures is important this can
* cause issues. This forgery can be blocked by all verifiers forcing signers
* to use a normalized form.
*
* The lower-S form reduces the size of signatures slightly on average when
* variable length encodings (such as DER) are used and is cheap to verify,
* making it a good choice. Security of always using lower-S is assured because
* anyone can trivially modify a signature after the fact to enforce this
* property anyway.
*
* The lower S value is always between 0x1 and
* 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0,
* inclusive.
*
* No other forms of ECDSA malleability are known and none seem likely, but
* there is no formal proof that ECDSA, even with this additional restriction,
* is free of other malleability. Commonly used serialization schemes will also
* accept various non-unique encodings, so care should be taken when this
* property is required for an application.
*
* The secp256k1_ecdsa_sign function will by default create signatures in the
* lower-S form, and secp256k1_ecdsa_verify will not accept others. In case
* signatures come from a system that cannot enforce this property,
* secp256k1_ecdsa_signature_normalize must be called before verification.
*/
SECP256K1_API int secp256k1_ecdsa_signature_normalize(
const secp256k1_context *ctx,
secp256k1_ecdsa_signature *sigout,
const secp256k1_ecdsa_signature *sigin
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(3);
/** An implementation of RFC6979 (using HMAC-SHA256) as nonce generation function.
* If a data pointer is passed, it is assumed to be a pointer to 32 bytes of
* extra entropy.
*/
SECP256K1_API const secp256k1_nonce_function secp256k1_nonce_function_rfc6979;
/** A default safe nonce generation function (currently equal to secp256k1_nonce_function_rfc6979). */
SECP256K1_API const secp256k1_nonce_function secp256k1_nonce_function_default;
/** Create an ECDSA signature.
*
* Returns: 1: signature created
* 0: the nonce generation function failed, or the secret key was invalid.
* Args: ctx: pointer to a context object (not secp256k1_context_static).
* Out: sig: pointer to an array where the signature will be placed.
* In: msghash32: the 32-byte message hash being signed.
* seckey: pointer to a 32-byte secret key.
* 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). If it is non-NULL and
* secp256k1_nonce_function_default is used, then ndata must be a
* pointer to 32-bytes of additional data.
*
* The created signature is always in lower-S form. See
* secp256k1_ecdsa_signature_normalize for more details.
*/
SECP256K1_API int secp256k1_ecdsa_sign(
const secp256k1_context *ctx,
secp256k1_ecdsa_signature *sig,
const unsigned char *msghash32,
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 an elliptic curve secret key.
*
* A secret key is valid if it is not 0 and less than the secp256k1 curve order
* when interpreted as an integer (most significant byte first). The
* probability of choosing a 32-byte string uniformly at random which is an
* invalid secret key is negligible. However, if it does happen it should
* be assumed that the randomness source is severely broken and there should
* be no retry.
*
* Returns: 1: secret key is valid
* 0: secret key is invalid
* Args: ctx: pointer to a context object.
* In: seckey: pointer to a 32-byte secret key.
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_verify(
const secp256k1_context *ctx,
const unsigned char *seckey
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
/** Compute the public key for a secret key.
*
* Returns: 1: secret was valid, public key stores.
* 0: secret was invalid, try again.
* Args: ctx: pointer to a context object (not secp256k1_context_static).
* Out: pubkey: pointer to the created public key.
* In: seckey: pointer to a 32-byte secret key.
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_create(
const secp256k1_context *ctx,
secp256k1_pubkey *pubkey,
const unsigned char *seckey
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
/** Negates a secret key in place.
*
* Returns: 0 if the given secret key is invalid according to
* secp256k1_ec_seckey_verify. 1 otherwise
* Args: ctx: pointer to a context object
* In/Out: seckey: pointer to the 32-byte secret key to be negated. If the
* secret key is invalid according to
* secp256k1_ec_seckey_verify, this function returns 0 and
* seckey will be set to some unspecified value.
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_negate(
const secp256k1_context *ctx,
unsigned char *seckey
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
/** Same as secp256k1_ec_seckey_negate, but DEPRECATED. Will be removed in
* future versions. */
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_negate(
const secp256k1_context *ctx,
unsigned char *seckey
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2)
SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_negate instead");
/** Negates a public key in place.
*
* Returns: 1 always
* Args: ctx: pointer to a context object
* In/Out: pubkey: pointer to the public key to be negated.
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_negate(
const secp256k1_context *ctx,
secp256k1_pubkey *pubkey
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
/** Tweak a secret key by adding tweak to it.
*
* Returns: 0 if the arguments are invalid or the resulting secret key would be
* invalid (only when the tweak is the negation of the secret key). 1
* otherwise.
* Args: ctx: pointer to a context object.
* In/Out: seckey: pointer to a 32-byte secret key. If the secret key is
* invalid according to secp256k1_ec_seckey_verify, this
* function returns 0. seckey will be set to some unspecified
* value if this function returns 0.
* In: tweak32: pointer to a 32-byte tweak, which must be valid according to
* secp256k1_ec_seckey_verify or 32 zero bytes. For uniformly
* random 32-byte tweaks, the chance of being invalid is
* negligible (around 1 in 2^128).
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_tweak_add(
const secp256k1_context *ctx,
unsigned char *seckey,
const unsigned char *tweak32
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
/** Same as secp256k1_ec_seckey_tweak_add, but DEPRECATED. Will be removed in
* future versions. */
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_add(
const secp256k1_context *ctx,
unsigned char *seckey,
const unsigned char *tweak32
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3)
SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_tweak_add instead");
/** Tweak a public key by adding tweak times the generator to it.
*
* Returns: 0 if the arguments are invalid or the resulting public key would be
* invalid (only when the tweak is the negation of the corresponding
* secret key). 1 otherwise.
* Args: ctx: pointer to a context object.
* In/Out: pubkey: pointer to a public key object. pubkey will be set to an
* invalid value if this function returns 0.
* In: tweak32: pointer to a 32-byte tweak, which must be valid according to
* secp256k1_ec_seckey_verify or 32 zero bytes. For uniformly
* random 32-byte tweaks, the chance of being invalid is
* negligible (around 1 in 2^128).
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_add(
const secp256k1_context *ctx,
secp256k1_pubkey *pubkey,
const unsigned char *tweak32
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
/** Tweak a secret key by multiplying it by a tweak.
*
* Returns: 0 if the arguments are invalid. 1 otherwise.
* Args: ctx: pointer to a context object.
* In/Out: seckey: pointer to a 32-byte secret key. If the secret key is
* invalid according to secp256k1_ec_seckey_verify, this
* function returns 0. seckey will be set to some unspecified
* value if this function returns 0.
* In: tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to
* secp256k1_ec_seckey_verify, this function returns 0. For
* uniformly random 32-byte arrays the chance of being invalid
* is negligible (around 1 in 2^128).
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_tweak_mul(
const secp256k1_context *ctx,
unsigned char *seckey,
const unsigned char *tweak32
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
/** Same as secp256k1_ec_seckey_tweak_mul, but DEPRECATED. Will be removed in
* future versions. */
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_mul(
const secp256k1_context *ctx,
unsigned char *seckey,
const unsigned char *tweak32
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3)
SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_tweak_mul instead");
/** Tweak a public key by multiplying it by a tweak value.
*
* Returns: 0 if the arguments are invalid. 1 otherwise.
* Args: ctx: pointer to a context object.
* In/Out: pubkey: pointer to a public key object. pubkey will be set to an
* invalid value if this function returns 0.
* In: tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to
* secp256k1_ec_seckey_verify, this function returns 0. For
* uniformly random 32-byte arrays the chance of being invalid
* is negligible (around 1 in 2^128).
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_mul(
const secp256k1_context *ctx,
secp256k1_pubkey *pubkey,
const unsigned char *tweak32
) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
/** Randomizes the context to provide enhanced protection against side-channel leakage.
*
* Returns: 1: randomization successful
* 0: error
* Args: ctx: pointer to a context object (not secp256k1_context_static).
* In: seed32: pointer to a 32-byte random seed (NULL resets to initial state).
*
* While secp256k1 code is written and tested to be constant-time no matter what
* secret values are, it is possible that a compiler may output code which is not,
* and also that the CPU may not emit the same radio frequencies or draw the same
* amount of power for all values. Randomization of the context shields against
* side-channel observations which aim to exploit secret-dependent behaviour in
* certain computations which involve secret keys.
*
* It is highly recommended to call this function on contexts returned from
* secp256k1_context_create or secp256k1_context_clone (or from the corresponding
* functions in secp256k1_preallocated.h) before using these contexts to call API
* functions that perform computations involving secret keys, e.g., signing and
* public key generation. It is possible to call this function more than once on
* the same context, and doing so before every few computations involving secret
* keys is recommended as a defense-in-depth measure. Randomization of the static
* context secp256k1_context_static is not supported.
*
* Currently, the random seed is mainly used for blinding multiplications of a
* secret scalar with the elliptic curve base point. Multiplications of this
* kind are performed by exactly those API functions which are documented to
* require a context that is not secp256k1_context_static. As a rule of thumb,
* these are all functions which take a secret key (or a keypair) as an input.
* A notable exception to that rule is the ECDH module, which relies on a different
* kind of elliptic curve point multiplication and thus does not benefit from
* enhanced protection against side-channel leakage currently.
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_context_randomize(
secp256k1_context *ctx,
const unsigned char *seed32
) SECP256K1_ARG_NONNULL(1);
/** Add a number of public keys together.
*
* Returns: 1: the sum of the public keys is valid.
* 0: the sum of the public keys is not valid.
* Args: ctx: pointer to a context object.
* Out: out: pointer to a public key object for placing the resulting public key.
* In: ins: pointer to array of pointers to public keys.
* n: the number of public keys to add together (must be at least 1).
*/
SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_combine(
const secp256k1_context *ctx,
secp256k1_pubkey *out,
const secp256k1_pubkey * const *ins,
size_t n
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