548 lines
24 KiB
C
548 lines
24 KiB
C
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#ifndef _SECP256K1_
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# define _SECP256K1_
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# ifdef __cplusplus
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extern "C" {
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# endif
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#include <stddef.h>
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/* These rules specify the order of arguments in API calls:
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*
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* 1. Context pointers go first, followed by output arguments, combined
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* output/input arguments, and finally input-only arguments.
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* 2. Array lengths always immediately the follow the argument whose length
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* they describe, even if this violates rule 1.
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* 3. Within the OUT/OUTIN/IN groups, pointers to data that is typically generated
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* later go first. This means: signatures, public nonces, private nonces,
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* messages, public keys, secret keys, tweaks.
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* 4. Arguments that are not data pointers go last, from more complex to less
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* complex: function pointers, algorithm names, messages, void pointers,
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* counts, flags, booleans.
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* 5. Opaque data pointers follow the function pointer they are to be passed to.
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*/
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/** Opaque data structure that holds context information (precomputed tables etc.).
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*
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* The purpose of context structures is to cache large precomputed data tables
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* that are expensive to construct, and also to maintain the randomization data
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* for blinding.
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*
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* Do not create a new context object for each operation, as construction is
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* far slower than all other API calls (~100 times slower than an ECDSA
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* verification).
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*
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* A constructed context can safely be used from multiple threads
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* simultaneously, but API call that take a non-const pointer to a context
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* need exclusive access to it. In particular this is the case for
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* secp256k1_context_destroy and secp256k1_context_randomize.
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*
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* Regarding randomization, either do it once at creation time (in which case
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* you do not need any locking for the other calls), or use a read-write lock.
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*/
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typedef struct secp256k1_context_struct secp256k1_context;
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/** Opaque data structure that holds a parsed and valid public key.
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*
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* The exact representation of data inside is implementation defined and not
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* guaranteed to be portable between different platforms or versions. It is
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* however guaranteed to be 64 bytes in size, and can be safely copied/moved.
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* If you need to convert to a format suitable for storage or transmission, use
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* secp256k1_ec_pubkey_serialize and secp256k1_ec_pubkey_parse.
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*
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* Furthermore, it is guaranteed that identical public keys (ignoring
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* compression) will have identical representation, so they can be memcmp'ed.
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*/
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typedef struct {
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unsigned char data[64];
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} secp256k1_pubkey;
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/** Opaque data structured that holds a parsed ECDSA signature.
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*
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* The exact representation of data inside is implementation defined and not
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* guaranteed to be portable between different platforms or versions. It is
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* however guaranteed to be 64 bytes in size, and can be safely copied/moved.
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* If you need to convert to a format suitable for storage or transmission, use
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* the secp256k1_ecdsa_signature_serialize_* and
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* secp256k1_ecdsa_signature_serialize_* functions.
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*
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* Furthermore, it is guaranteed to identical signatures will have identical
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* representation, so they can be memcmp'ed.
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*/
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typedef struct {
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unsigned char data[64];
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} secp256k1_ecdsa_signature;
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/** A pointer to a function to deterministically generate a nonce.
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*
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* Returns: 1 if a nonce was successfully generated. 0 will cause signing to fail.
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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 (will not be NULL)
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* key32: pointer to a 32-byte secret key (will not be NULL)
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* algo16: pointer to a 16-byte array describing the signature
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* algorithm (will be NULL for ECDSA for compatibility).
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* data: Arbitrary data pointer that is passed through.
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* attempt: how many iterations we have tried to find a nonce.
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* This will almost always be 0, but different attempt values
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* are required to result in a different nonce.
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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 algorithm, the key and the attempt.
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*/
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typedef int (*secp256k1_nonce_function)(
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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 *algo16,
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void *data,
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unsigned int attempt
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);
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# if !defined(SECP256K1_GNUC_PREREQ)
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# if defined(__GNUC__)&&defined(__GNUC_MINOR__)
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# define SECP256K1_GNUC_PREREQ(_maj,_min) \
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((__GNUC__<<16)+__GNUC_MINOR__>=((_maj)<<16)+(_min))
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# else
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# define SECP256K1_GNUC_PREREQ(_maj,_min) 0
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# endif
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# endif
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# if (!defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L) )
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# if SECP256K1_GNUC_PREREQ(2,7)
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# define SECP256K1_INLINE __inline__
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# elif (defined(_MSC_VER))
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# define SECP256K1_INLINE __inline
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# else
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# define SECP256K1_INLINE
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# endif
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# else
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# define SECP256K1_INLINE inline
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# endif
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#ifndef SECP256K1_API
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# if defined(_WIN32)
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# ifdef SECP256K1_BUILD
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# define SECP256K1_API __declspec(dllexport)
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# else
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# define SECP256K1_API
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# endif
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# elif defined(__GNUC__) && defined(SECP256K1_BUILD)
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# define SECP256K1_API __attribute__ ((visibility ("default")))
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# else
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# define SECP256K1_API
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# endif
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#endif
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/**Warning attributes
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* NONNULL is not used if SECP256K1_BUILD is set to avoid the compiler optimizing out
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* some paranoid null checks. */
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# if defined(__GNUC__) && SECP256K1_GNUC_PREREQ(3, 4)
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# define SECP256K1_WARN_UNUSED_RESULT __attribute__ ((__warn_unused_result__))
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# else
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# define SECP256K1_WARN_UNUSED_RESULT
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# endif
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# if !defined(SECP256K1_BUILD) && defined(__GNUC__) && SECP256K1_GNUC_PREREQ(3, 4)
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# define SECP256K1_ARG_NONNULL(_x) __attribute__ ((__nonnull__(_x)))
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# else
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# define SECP256K1_ARG_NONNULL(_x)
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# endif
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/** Flags to pass to secp256k1_context_create. */
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# define SECP256K1_CONTEXT_VERIFY (1 << 0)
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# define SECP256K1_CONTEXT_SIGN (1 << 1)
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/** Flag to pass to secp256k1_ec_pubkey_serialize and secp256k1_ec_privkey_export. */
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# define SECP256K1_EC_COMPRESSED (1 << 0)
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/** Create a secp256k1 context object.
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*
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* Returns: a newly created context object.
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* In: flags: which parts of the context to initialize.
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*/
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SECP256K1_API secp256k1_context* secp256k1_context_create(
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unsigned int flags
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) SECP256K1_WARN_UNUSED_RESULT;
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/** Copies a secp256k1 context object.
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*
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* Returns: a newly created context object.
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* Args: ctx: an existing context to copy (cannot be NULL)
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*/
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SECP256K1_API secp256k1_context* secp256k1_context_clone(
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const secp256k1_context* ctx
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) SECP256K1_ARG_NONNULL(1) SECP256K1_WARN_UNUSED_RESULT;
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/** Destroy a secp256k1 context object.
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*
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* The context pointer may not be used afterwards.
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* Args: ctx: an existing context to destroy (cannot be NULL)
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*/
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SECP256K1_API void secp256k1_context_destroy(
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secp256k1_context* ctx
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);
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/** Set a callback function to be called when an illegal argument is passed to
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* an API call. It will only trigger for violations that are mentioned
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* explicitly in the header.
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*
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* The philosophy is that these shouldn't be dealt with through a
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* specific return value, as calling code should not have branches to deal with
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* the case that this code itself is broken.
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*
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* On the other hand, during debug stage, one would want to be informed about
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* such mistakes, and the default (crashing) may be inadvisable.
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* When this callback is triggered, the API function called is guaranteed not
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* to cause a crash, though its return value and output arguments are
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* undefined.
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*
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* Args: ctx: an existing context object (cannot be NULL)
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* In: fun: a pointer to a function to call when an illegal argument is
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* passed to the API, taking a message and an opaque pointer
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* (NULL restores a default handler that calls abort).
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* data: the opaque pointer to pass to fun above.
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*/
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SECP256K1_API void secp256k1_context_set_illegal_callback(
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secp256k1_context* ctx,
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void (*fun)(const char* message, void* data),
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const void* data
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) SECP256K1_ARG_NONNULL(1);
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/** Set a callback function to be called when an internal consistency check
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* fails. The default is crashing.
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*
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* This can only trigger in case of a hardware failure, miscompilation,
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* memory corruption, serious bug in the library, or other error would can
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* otherwise result in undefined behaviour. It will not trigger due to mere
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* incorrect usage of the API (see secp256k1_context_set_illegal_callback
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* for that). After this callback returns, anything may happen, including
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* crashing.
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*
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* Args: ctx: an existing context object (cannot be NULL)
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* In: fun: a pointer to a function to call when an interal error occurs,
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* taking a message and an opaque pointer (NULL restores a default
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* handler that calls abort).
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* data: the opaque pointer to pass to fun above.
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*/
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SECP256K1_API void secp256k1_context_set_error_callback(
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secp256k1_context* ctx,
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void (*fun)(const char* message, void* data),
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const void* data
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) SECP256K1_ARG_NONNULL(1);
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/** Parse a variable-length public key into the pubkey object.
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*
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* Returns: 1 if the public key was fully valid.
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* 0 if the public key could not be parsed or is invalid.
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* Args: ctx: a secp256k1 context object.
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* Out: pubkey: pointer to a pubkey object. If 1 is returned, it is set to a
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* parsed version of input. If not, its value is undefined.
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* In: input: pointer to a serialized public key
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* inputlen: length of the array pointed to by input
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*
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* This function supports parsing compressed (33 bytes, header byte 0x02 or
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* 0x03), uncompressed (65 bytes, header byte 0x04), or hybrid (65 bytes, header
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* byte 0x06 or 0x07) format public keys.
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*/
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SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_parse(
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const secp256k1_context* ctx,
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secp256k1_pubkey* pubkey,
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const unsigned char *input,
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size_t inputlen
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
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/** Serialize a pubkey object into a serialized byte sequence.
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*
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* Returns: 1 always.
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* Args: ctx: a secp256k1 context object.
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* Out: output: a pointer to a 65-byte (if compressed==0) or 33-byte (if
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* compressed==1) byte array to place the serialized key in.
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* outputlen: a pointer to an integer which will contain the serialized
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* size.
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* In: pubkey: a pointer to a secp256k1_pubkey containing an initialized
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* public key.
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* flags: SECP256K1_EC_COMPRESSED if serialization should be in
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* compressed format.
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*/
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SECP256K1_API int secp256k1_ec_pubkey_serialize(
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const secp256k1_context* ctx,
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unsigned char *output,
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size_t *outputlen,
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const secp256k1_pubkey* pubkey,
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unsigned int flags
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
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/** Parse a DER ECDSA signature.
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*
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* Returns: 1 when the signature could be parsed, 0 otherwise.
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* Args: ctx: a secp256k1 context object
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* Out: sig: a pointer to a signature object
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* In: input: a pointer to the signature to be parsed
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* inputlen: the length of the array pointed to be input
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*
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* Note that this function also supports some violations of DER and even BER.
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*/
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SECP256K1_API int secp256k1_ecdsa_signature_parse_der(
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const secp256k1_context* ctx,
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secp256k1_ecdsa_signature* sig,
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const unsigned char *input,
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size_t inputlen
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
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/** Serialize an ECDSA signature in DER format.
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*
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* Returns: 1 if enough space was available to serialize, 0 otherwise
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* Args: ctx: a secp256k1 context object
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* Out: output: a pointer to an array to store the DER serialization
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* In/Out: outputlen: a pointer to a length integer. Initially, this integer
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* should be set to the length of output. After the call
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* it will be set to the length of the serialization (even
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* if 0 was returned).
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* In: sig: a pointer to an initialized signature object
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*/
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SECP256K1_API int secp256k1_ecdsa_signature_serialize_der(
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const secp256k1_context* ctx,
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unsigned char *output,
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size_t *outputlen,
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const secp256k1_ecdsa_signature* sig
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
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/** Verify an ECDSA signature.
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*
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* Returns: 1: correct signature
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* 0: incorrect or unparseable signature
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* Args: ctx: a secp256k1 context object, initialized for verification.
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* In: sig: the signature being verified (cannot be NULL)
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* msg32: the 32-byte message hash being verified (cannot be NULL)
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* pubkey: pointer to an initialized public key to verify with (cannot be NULL)
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*/
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SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdsa_verify(
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const secp256k1_context* ctx,
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const secp256k1_ecdsa_signature *sig,
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const unsigned char *msg32,
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const secp256k1_pubkey *pubkey
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
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/** An implementation of RFC6979 (using HMAC-SHA256) as nonce generation function.
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* If a data pointer is passed, it is assumed to be a pointer to 32 bytes of
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* extra entropy.
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*/
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extern const secp256k1_nonce_function secp256k1_nonce_function_rfc6979;
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/** A default safe nonce generation function (currently equal to secp256k1_nonce_function_rfc6979). */
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extern const secp256k1_nonce_function secp256k1_nonce_function_default;
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/** Create an ECDSA signature.
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*
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* Returns: 1: signature created
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* 0: the nonce generation function failed, or the private key was invalid.
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* Args: ctx: pointer to a context object, initialized for signing (cannot be NULL)
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* Out: sig: pointer to an array where the signature will be placed (cannot be NULL)
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* In: msg32: the 32-byte message hash being signed (cannot be NULL)
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* seckey: pointer to a 32-byte secret key (cannot be NULL)
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* noncefp:pointer to a nonce generation function. If NULL, secp256k1_nonce_function_default is used
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* ndata: pointer to arbitrary data used by the nonce generation function (can be NULL)
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*
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* The sig always has an s value in the lower half of the range (From 0x1
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* to 0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0,
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* inclusive), unlike many other implementations.
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*
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* With ECDSA a third-party can can forge a second distinct signature
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* of the same message given a single initial signature without knowing
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* the key by setting s to its additive inverse mod-order, 'flipping' the
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* sign of the random point R which is not included in the signature.
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* Since the forgery is of the same message this isn't universally
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* problematic, but in systems where message malleability or uniqueness
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* of signatures is important this can cause issues. This forgery can be
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* blocked by all verifiers forcing signers to use a canonical form. The
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* lower-S form reduces the size of signatures slightly on average when
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* variable length encodings (such as DER) are used and is cheap to
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* verify, making it a good choice. Security of always using lower-S is
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* assured because anyone can trivially modify a signature after the
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* fact to enforce this property. Adjusting it inside the signing
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* function avoids the need to re-serialize or have curve specific
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* constants outside of the library. By always using a canonical form
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* even in applications where it isn't needed it becomes possible to
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* impose a requirement later if a need is discovered.
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* No other forms of ECDSA malleability are known and none seem likely,
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* but there is no formal proof that ECDSA, even with this additional
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* restriction, is free of other malleability. Commonly used serialization
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* schemes will also accept various non-unique encodings, so care should
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* be taken when this property is required for an application.
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*/
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SECP256K1_API int secp256k1_ecdsa_sign(
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const secp256k1_context* ctx,
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secp256k1_ecdsa_signature *sig,
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const unsigned char *msg32,
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const unsigned char *seckey,
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secp256k1_nonce_function noncefp,
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const void *ndata
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
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/** Verify an ECDSA secret key.
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*
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* Returns: 1: secret key is valid
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* 0: secret key is invalid
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* Args: ctx: pointer to a context object (cannot be NULL)
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* In: seckey: pointer to a 32-byte secret key (cannot be NULL)
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*/
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SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_verify(
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const secp256k1_context* ctx,
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const unsigned char *seckey
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
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/** Compute the public key for a secret key.
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*
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* Returns: 1: secret was valid, public key stores
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* 0: secret was invalid, try again
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* Args: ctx: pointer to a context object, initialized for signing (cannot be NULL)
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* Out: pubkey: pointer to the created public key (cannot be NULL)
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* In: seckey: pointer to a 32-byte private key (cannot be NULL)
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*/
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SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_create(
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const secp256k1_context* ctx,
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secp256k1_pubkey *pubkey,
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const unsigned char *seckey
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
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/** Export a private key in BER format.
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*
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* Returns: 1 if the private key was valid.
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* Args: ctx: pointer to a context object, initialized for signing (cannot
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* be NULL)
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* Out: privkey: pointer to an array for storing the private key in BER.
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* Should have space for 279 bytes, and cannot be NULL.
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* privkeylen: Pointer to an int where the length of the private key in
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* privkey will be stored.
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* In: seckey: pointer to a 32-byte secret key to export.
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* flags: SECP256K1_EC_COMPRESSED if the key should be exported in
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* compressed format.
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*
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* This function is purely meant for compatibility with applications that
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* require BER encoded keys. When working with secp256k1-specific code, the
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* simple 32-byte private keys are sufficient.
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*
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* Note that this function does not guarantee correct DER output. It is
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* guaranteed to be parsable by secp256k1_ec_privkey_import.
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*/
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SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_export(
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const secp256k1_context* ctx,
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unsigned char *privkey,
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size_t *privkeylen,
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const unsigned char *seckey,
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unsigned int flags
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
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/** Import a private key in DER format.
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* Returns: 1 if a private key was extracted.
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* Args: ctx: pointer to a context object (cannot be NULL).
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* Out: seckey: pointer to a 32-byte array for storing the private key.
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* (cannot be NULL).
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* In: privkey: pointer to a private key in DER format (cannot be NULL).
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* privkeylen: length of the DER private key pointed to be privkey.
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*
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* This function will accept more than just strict DER, and even allow some BER
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* violations. The public key stored inside the DER-encoded private key is not
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* verified for correctness, nor are the curve parameters. Use this function
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* only if you know in advance it is supposed to contain a secp256k1 private
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* key.
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*/
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SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_import(
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const secp256k1_context* ctx,
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unsigned char *seckey,
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const unsigned char *privkey,
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size_t privkeylen
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
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/** Tweak a private key by adding tweak to it.
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* Returns: 0 if the tweak was out of range (chance of around 1 in 2^128 for
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* uniformly random 32-byte arrays, or if the resulting private key
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* would be invalid (only when the tweak is the complement of the
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* private key). 1 otherwise.
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* Args: ctx: pointer to a context object (cannot be NULL).
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* In/Out: seckey: pointer to a 32-byte private key.
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* In: tweak: pointer to a 32-byte tweak.
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*/
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SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_add(
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const secp256k1_context* ctx,
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unsigned char *seckey,
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const unsigned char *tweak
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
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/** Tweak a public key by adding tweak times the generator to it.
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* Returns: 0 if the tweak was out of range (chance of around 1 in 2^128 for
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* uniformly random 32-byte arrays, or if the resulting public key
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* would be invalid (only when the tweak is the complement of the
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* corresponding private key). 1 otherwise.
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* Args: ctx: pointer to a context object initialized for validation
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* (cannot be NULL).
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* In/Out: pubkey: pointer to a public key object.
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* In: tweak: pointer to a 32-byte tweak.
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*/
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SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_add(
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const secp256k1_context* ctx,
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secp256k1_pubkey *pubkey,
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const unsigned char *tweak
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
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/** Tweak a private key by multiplying it by a tweak.
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* Returns: 0 if the tweak was out of range (chance of around 1 in 2^128 for
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* uniformly random 32-byte arrays, or equal to zero. 1 otherwise.
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* Args: ctx: pointer to a context object (cannot be NULL).
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* In/Out: seckey: pointer to a 32-byte private key.
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* In: tweak: pointer to a 32-byte tweak.
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*/
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SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_mul(
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const secp256k1_context* ctx,
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unsigned char *seckey,
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const unsigned char *tweak
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
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/** Tweak a public key by multiplying it by a tweak value.
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* Returns: 0 if the tweak was out of range (chance of around 1 in 2^128 for
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* uniformly random 32-byte arrays, or equal to zero. 1 otherwise.
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* Args: ctx: pointer to a context object initialized for validation
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* (cannot be NULL).
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* In/Out: pubkey: pointer to a public key obkect.
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* In: tweak: pointer to a 32-byte tweak.
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*/
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SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_mul(
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const secp256k1_context* ctx,
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secp256k1_pubkey *pubkey,
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const unsigned char *tweak
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) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
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/** Updates the context randomization.
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* Returns: 1: randomization successfully updated
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* 0: error
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* Args: ctx: pointer to a context object (cannot be NULL)
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* In: seed32: pointer to a 32-byte random seed (NULL resets to initial state)
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*/
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SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_context_randomize(
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secp256k1_context* ctx,
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const unsigned char *seed32
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) SECP256K1_ARG_NONNULL(1);
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/** Add a number of public keys together.
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* Returns: 1: the sum of the public keys is valid.
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* 0: the sum of the public keys is not valid.
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* Args: ctx: pointer to a context object
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* Out: out: pointer to pubkey for placing the resulting public key
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* (cannot be NULL)
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* In: ins: pointer to array of pointers to public keys (cannot be NULL)
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* n: the number of public keys to add together (must be at least 1)
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* Use secp256k1_ec_pubkey_compress and secp256k1_ec_pubkey_decompress if the
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* uncompressed format is needed.
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*/
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SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_combine(
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const secp256k1_context* ctx,
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secp256k1_pubkey *out,
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const secp256k1_pubkey * const * ins,
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int n
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) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
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# ifdef __cplusplus
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}
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# endif
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#endif
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