csecp256k1

secp256k1.h (45171B)

---

 #ifndef SECP256K1_H
 #define SECP256K1_H
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 #include <stddef.h>
 
 /** Unless explicitly stated all pointer arguments must not be NULL.
  *
  * The following rules specify the order of arguments in API calls:
  *
  * 1. Context pointers go first, followed by output arguments, combined
  *    output/input arguments, and finally input-only arguments.
  * 2. Array lengths always immediately follow the argument whose length
  *    they describe, even if this violates rule 1.
  * 3. Within the OUT/OUTIN/IN groups, pointers to data that is typically generated
  *    later go first. This means: signatures, public nonces, secret nonces,
  *    messages, public keys, secret keys, tweaks.
  * 4. Arguments that are not data pointers go last, from more complex to less
  *    complex: function pointers, algorithm names, messages, void pointers,
  *    counts, flags, booleans.
  * 5. Opaque data pointers follow the function pointer they are to be passed to.
  */
 
 /** Opaque data structure that holds context information
  *
  *  The primary purpose of context objects is to store randomization data for
  *  enhanced protection against side-channel leakage. This protection is only
  *  effective if the context is randomized after its creation. See
  *  haskellsecp256k1_v0_1_0_context_create for creation of contexts and
  *  haskellsecp256k1_v0_1_0_context_randomize for randomization.
  *
  *  A secondary purpose of context objects is to store pointers to callback
  *  functions that the library will call when certain error states arise. See
  *  haskellsecp256k1_v0_1_0_context_set_error_callback as well as
  *  haskellsecp256k1_v0_1_0_context_set_illegal_callback for details. Future library versions
  *  may use context objects for additional purposes.
  *
  *  A constructed context can safely be used from multiple threads
  *  simultaneously, but API calls that take a non-const pointer to a context
  *  need exclusive access to it. In particular this is the case for
  *  haskellsecp256k1_v0_1_0_context_destroy, haskellsecp256k1_v0_1_0_context_preallocated_destroy,
  *  and haskellsecp256k1_v0_1_0_context_randomize.
  *
  *  Regarding randomization, either do it once at creation time (in which case
  *  you do not need any locking for the other calls), or use a read-write lock.
  */
 typedef struct haskellsecp256k1_v0_1_0_context_struct haskellsecp256k1_v0_1_0_context;
 
 /** Opaque data structure that holds rewritable "scratch space"
  *
  *  The purpose of this structure is to replace dynamic memory allocations,
  *  because we target architectures where this may not be available. It is
  *  essentially a resizable (within specified parameters) block of bytes,
  *  which is initially created either by memory allocation or TODO as a pointer
  *  into some fixed rewritable space.
  *
  *  Unlike the context object, this cannot safely be shared between threads
  *  without additional synchronization logic.
  */
 typedef struct haskellsecp256k1_v0_1_0_scratch_space_struct haskellsecp256k1_v0_1_0_scratch_space;
 
 /** Opaque data structure that holds a parsed and valid public key.
  *
  *  The exact representation of data inside is implementation defined and not
  *  guaranteed to be portable between different platforms or versions. It is
  *  however guaranteed to be 64 bytes in size, and can be safely copied/moved.
  *  If you need to convert to a format suitable for storage or transmission,
  *  use haskellsecp256k1_v0_1_0_ec_pubkey_serialize and haskellsecp256k1_v0_1_0_ec_pubkey_parse. To
  *  compare keys, use haskellsecp256k1_v0_1_0_ec_pubkey_cmp.
  */
 typedef struct {
     unsigned char data[64];
 } haskellsecp256k1_v0_1_0_pubkey;
 
 /** Opaque data structured that holds a parsed ECDSA signature.
  *
  *  The exact representation of data inside is implementation defined and not
  *  guaranteed to be portable between different platforms or versions. It is
  *  however guaranteed to be 64 bytes in size, and can be safely copied/moved.
  *  If you need to convert to a format suitable for storage, transmission, or
  *  comparison, use the haskellsecp256k1_v0_1_0_ecdsa_signature_serialize_* and
  *  haskellsecp256k1_v0_1_0_ecdsa_signature_parse_* functions.
  */
 typedef struct {
     unsigned char data[64];
 } haskellsecp256k1_v0_1_0_ecdsa_signature;
 
 /** A pointer to a function to deterministically generate a nonce.
  *
  * Returns: 1 if a nonce was successfully generated. 0 will cause signing to fail.
  * 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)
  *          algo16:    pointer to a 16-byte array describing the signature
  *                     algorithm (will be NULL for ECDSA for compatibility).
  *          data:      Arbitrary data pointer that is passed through.
  *          attempt:   how many iterations we have tried to find a nonce.
  *                     This will almost always be 0, but different attempt values
  *                     are required to result in a different nonce.
  *
  * Except for test cases, this function should compute some cryptographic hash of
  * the message, the algorithm, the key and the attempt.
  */
 typedef int (*haskellsecp256k1_v0_1_0_nonce_function)(
     unsigned char *nonce32,
     const unsigned char *msg32,
     const unsigned char *key32,
     const unsigned char *algo16,
     void *data,
     unsigned int attempt
 );
 
 # if !defined(SECP256K1_GNUC_PREREQ)
 #  if defined(__GNUC__)&&defined(__GNUC_MINOR__)
 #   define SECP256K1_GNUC_PREREQ(_maj,_min) \
  ((__GNUC__<<16)+__GNUC_MINOR__>=((_maj)<<16)+(_min))
 #  else
 #   define SECP256K1_GNUC_PREREQ(_maj,_min) 0
 #  endif
 # endif
 
 /*  When this header is used at build-time the SECP256K1_BUILD define needs to be set
  *  to correctly setup export attributes and nullness checks.  This is normally done
  *  by secp256k1.c but to guard against this header being included before secp256k1.c
  *  has had a chance to set the define (e.g. via test harnesses that just includes
  *  secp256k1.c) we set SECP256K1_NO_BUILD when this header is processed without the
  *  BUILD define so this condition can be caught.
  */
 #ifndef SECP256K1_BUILD
 # define SECP256K1_NO_BUILD
 #endif
 
 /* Symbol visibility. */
 #if defined(_WIN32)
   /* GCC for Windows (e.g., MinGW) accepts the __declspec syntax
    * for MSVC compatibility. A __declspec declaration implies (but is not
    * exactly equivalent to) __attribute__ ((visibility("default"))), and so we
    * actually want __declspec even on GCC, see "Microsoft Windows Function
    * Attributes" in the GCC manual and the recommendations in
    * https://gcc.gnu.org/wiki/Visibility. */
 # if defined(SECP256K1_BUILD)
 #  if defined(DLL_EXPORT) || defined(SECP256K1_DLL_EXPORT)
     /* Building libsecp256k1 as a DLL.
      * 1. If using Libtool, it defines DLL_EXPORT automatically.
      * 2. In other cases, SECP256K1_DLL_EXPORT must be defined. */
 #   define SECP256K1_API extern __declspec (dllexport)
 #  endif
   /* The user must define SECP256K1_STATIC when consuming libsecp256k1 as a static
    * library on Windows. */
 # elif !defined(SECP256K1_STATIC)
    /* Consuming libsecp256k1 as a DLL. */
 #  define SECP256K1_API extern __declspec (dllimport)
 # endif
 #endif
 #ifndef SECP256K1_API
 # if defined(__GNUC__) && (__GNUC__ >= 4) && defined(SECP256K1_BUILD)
    /* Building libsecp256k1 on non-Windows using GCC or compatible. */
 #  define SECP256K1_API extern __attribute__ ((visibility ("default")))
 # else
    /* All cases not captured above. */
 #  define SECP256K1_API extern
 # endif
 #endif
 
 /* Warning attributes
  * NONNULL is not used if SECP256K1_BUILD is set to avoid the compiler optimizing out
  * some paranoid null checks. */
 # if defined(__GNUC__) && SECP256K1_GNUC_PREREQ(3, 4)
 #  define SECP256K1_WARN_UNUSED_RESULT __attribute__ ((__warn_unused_result__))
 # else
 #  define SECP256K1_WARN_UNUSED_RESULT
 # endif
 # if !defined(SECP256K1_BUILD) && defined(__GNUC__) && SECP256K1_GNUC_PREREQ(3, 4)
 #  define SECP256K1_ARG_NONNULL(_x)  __attribute__ ((__nonnull__(_x)))
 # else
 #  define SECP256K1_ARG_NONNULL(_x)
 # endif
 
 /* Attribute for marking functions, types, and variables as deprecated */
 #if !defined(SECP256K1_BUILD) && defined(__has_attribute)
 # if __has_attribute(__deprecated__)
 #  define SECP256K1_DEPRECATED(_msg) __attribute__ ((__deprecated__(_msg)))
 # else
 #  define SECP256K1_DEPRECATED(_msg)
 # endif
 #else
 # define SECP256K1_DEPRECATED(_msg)
 #endif
 
 /* All flags' lower 8 bits indicate what they're for. Do not use directly. */
 #define SECP256K1_FLAGS_TYPE_MASK ((1 << 8) - 1)
 #define SECP256K1_FLAGS_TYPE_CONTEXT (1 << 0)
 #define SECP256K1_FLAGS_TYPE_COMPRESSION (1 << 1)
 /* The higher bits contain the actual data. Do not use directly. */
 #define SECP256K1_FLAGS_BIT_CONTEXT_VERIFY (1 << 8)
 #define SECP256K1_FLAGS_BIT_CONTEXT_SIGN (1 << 9)
 #define SECP256K1_FLAGS_BIT_CONTEXT_DECLASSIFY (1 << 10)
 #define SECP256K1_FLAGS_BIT_COMPRESSION (1 << 8)
 
 /** Context flags to pass to haskellsecp256k1_v0_1_0_context_create, haskellsecp256k1_v0_1_0_context_preallocated_size, and
  *  haskellsecp256k1_v0_1_0_context_preallocated_create. */
 #define SECP256K1_CONTEXT_NONE (SECP256K1_FLAGS_TYPE_CONTEXT)
 
 /** Deprecated context flags. These flags are treated equivalent to SECP256K1_CONTEXT_NONE. */
 #define SECP256K1_CONTEXT_VERIFY (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_VERIFY)
 #define SECP256K1_CONTEXT_SIGN (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_SIGN)
 
 /* Testing flag. Do not use. */
 #define SECP256K1_CONTEXT_DECLASSIFY (SECP256K1_FLAGS_TYPE_CONTEXT | SECP256K1_FLAGS_BIT_CONTEXT_DECLASSIFY)
 
 /** Flag to pass to haskellsecp256k1_v0_1_0_ec_pubkey_serialize. */
 #define SECP256K1_EC_COMPRESSED (SECP256K1_FLAGS_TYPE_COMPRESSION | SECP256K1_FLAGS_BIT_COMPRESSION)
 #define SECP256K1_EC_UNCOMPRESSED (SECP256K1_FLAGS_TYPE_COMPRESSION)
 
 /** Prefix byte used to tag various encoded curvepoints for specific purposes */
 #define SECP256K1_TAG_PUBKEY_EVEN 0x02
 #define SECP256K1_TAG_PUBKEY_ODD 0x03
 #define SECP256K1_TAG_PUBKEY_UNCOMPRESSED 0x04
 #define SECP256K1_TAG_PUBKEY_HYBRID_EVEN 0x06
 #define SECP256K1_TAG_PUBKEY_HYBRID_ODD 0x07
 
 /** A built-in constant secp256k1 context object with static storage duration, to be
  *  used in conjunction with haskellsecp256k1_v0_1_0_selftest.
  *
  *  This context object offers *only limited functionality* , i.e., it cannot be used
  *  for API functions that perform computations involving secret keys, e.g., signing
  *  and public key generation. If this restriction applies to a specific API function,
  *  it is mentioned in its documentation. See haskellsecp256k1_v0_1_0_context_create if you need a
  *  full context object that supports all functionality offered by the library.
  *
  *  It is highly recommended to call haskellsecp256k1_v0_1_0_selftest before using this context.
  */
 SECP256K1_API const haskellsecp256k1_v0_1_0_context *haskellsecp256k1_v0_1_0_context_static;
 
 /** Deprecated alias for haskellsecp256k1_v0_1_0_context_static. */
 SECP256K1_API const haskellsecp256k1_v0_1_0_context *haskellsecp256k1_v0_1_0_context_no_precomp
 SECP256K1_DEPRECATED("Use haskellsecp256k1_v0_1_0_context_static instead");
 
 /** Perform basic self tests (to be used in conjunction with haskellsecp256k1_v0_1_0_context_static)
  *
  *  This function performs self tests that detect some serious usage errors and
  *  similar conditions, e.g., when the library is compiled for the wrong endianness.
  *  This is a last resort measure to be used in production. The performed tests are
  *  very rudimentary and are not intended as a replacement for running the test
  *  binaries.
  *
  *  It is highly recommended to call this before using haskellsecp256k1_v0_1_0_context_static.
  *  It is not necessary to call this function before using a context created with
  *  haskellsecp256k1_v0_1_0_context_create (or haskellsecp256k1_v0_1_0_context_preallocated_create), which will
  *  take care of performing the self tests.
  *
  *  If the tests fail, this function will call the default error handler to abort the
  *  program (see haskellsecp256k1_v0_1_0_context_set_error_callback).
  */
 SECP256K1_API void haskellsecp256k1_v0_1_0_selftest(void);
 
 
 /** Create a secp256k1 context object (in dynamically allocated memory).
  *
  *  This function uses malloc to allocate memory. It is guaranteed that malloc is
  *  called at most once for every call of this function. If you need to avoid dynamic
  *  memory allocation entirely, see haskellsecp256k1_v0_1_0_context_static and the functions in
  *  haskellsecp256k1_v0_1_0_preallocated.h.
  *
  *  Returns: pointer to a newly created context object.
  *  In:      flags: Always set to SECP256K1_CONTEXT_NONE (see below).
  *
  *  The only valid non-deprecated flag in recent library versions is
  *  SECP256K1_CONTEXT_NONE, which will create a context sufficient for all functionality
  *  offered by the library. All other (deprecated) flags will be treated as equivalent
  *  to the SECP256K1_CONTEXT_NONE flag. Though the flags parameter primarily exists for
  *  historical reasons, future versions of the library may introduce new flags.
  *
  *  If the context is intended to be used for API functions that perform computations
  *  involving secret keys, e.g., signing and public key generation, then it is highly
  *  recommended to call haskellsecp256k1_v0_1_0_context_randomize on the context before calling
  *  those API functions. This will provide enhanced protection against side-channel
  *  leakage, see haskellsecp256k1_v0_1_0_context_randomize for details.
  *
  *  Do not create a new context object for each operation, as construction and
  *  randomization can take non-negligible time.
  */
 SECP256K1_API haskellsecp256k1_v0_1_0_context *haskellsecp256k1_v0_1_0_context_create(
     unsigned int flags
 ) SECP256K1_WARN_UNUSED_RESULT;
 
 /** Copy a secp256k1 context object (into dynamically allocated memory).
  *
  *  This function uses malloc to allocate memory. It is guaranteed that malloc is
  *  called at most once for every call of this function. If you need to avoid dynamic
  *  memory allocation entirely, see the functions in haskellsecp256k1_v0_1_0_preallocated.h.
  *
  *  Cloning haskellsecp256k1_v0_1_0_context_static is not possible, and should not be emulated by
  *  the caller (e.g., using memcpy). Create a new context instead.
  *
  *  Returns: pointer to a newly created context object.
  *  Args:    ctx: pointer to a context to copy (not haskellsecp256k1_v0_1_0_context_static).
  */
 SECP256K1_API haskellsecp256k1_v0_1_0_context *haskellsecp256k1_v0_1_0_context_clone(
     const haskellsecp256k1_v0_1_0_context *ctx
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_WARN_UNUSED_RESULT;
 
 /** Destroy a secp256k1 context object (created in dynamically allocated memory).
  *
  *  The context pointer may not be used afterwards.
  *
  *  The context to destroy must have been created using haskellsecp256k1_v0_1_0_context_create
  *  or haskellsecp256k1_v0_1_0_context_clone. If the context has instead been created using
  *  haskellsecp256k1_v0_1_0_context_preallocated_create or haskellsecp256k1_v0_1_0_context_preallocated_clone, the
  *  behaviour is undefined. In that case, haskellsecp256k1_v0_1_0_context_preallocated_destroy must
  *  be used instead.
  *
  *  Args:   ctx: pointer to a context to destroy, constructed using
  *               haskellsecp256k1_v0_1_0_context_create or haskellsecp256k1_v0_1_0_context_clone
  *               (i.e., not haskellsecp256k1_v0_1_0_context_static).
  */
 SECP256K1_API void haskellsecp256k1_v0_1_0_context_destroy(
     haskellsecp256k1_v0_1_0_context *ctx
 ) SECP256K1_ARG_NONNULL(1);
 
 /** Set a callback function to be called when an illegal argument is passed to
  *  an API call. It will only trigger for violations that are mentioned
  *  explicitly in the header.
  *
  *  The philosophy is that these shouldn't be dealt with through a
  *  specific return value, as calling code should not have branches to deal with
  *  the case that this code itself is broken.
  *
  *  On the other hand, during debug stage, one would want to be informed about
  *  such mistakes, and the default (crashing) may be inadvisable.
  *  When this callback is triggered, the API function called is guaranteed not
  *  to cause a crash, though its return value and output arguments are
  *  undefined.
  *
  *  When this function has not been called (or called with fn==NULL), then the
  *  default handler will be used. The library provides a default handler which
  *  writes the message to stderr and calls abort. This default handler can be
  *  replaced at link time if the preprocessor macro
  *  USE_EXTERNAL_DEFAULT_CALLBACKS is defined, which is the case if the build
  *  has been configured with --enable-external-default-callbacks. Then the
  *  following two symbols must be provided to link against:
  *   - void haskellsecp256k1_v0_1_0_default_illegal_callback_fn(const char *message, void *data);
  *   - void haskellsecp256k1_v0_1_0_default_error_callback_fn(const char *message, void *data);
  *  The library can call these default handlers even before a proper callback data
  *  pointer could have been set using haskellsecp256k1_v0_1_0_context_set_illegal_callback or
  *  haskellsecp256k1_v0_1_0_context_set_error_callback, e.g., when the creation of a context
  *  fails. In this case, the corresponding default handler will be called with
  *  the data pointer argument set to NULL.
  *
  *  Args: ctx:  pointer to a context object.
  *  In:   fun:  pointer to a function to call when an illegal argument is
  *              passed to the API, taking a message and an opaque pointer.
  *              (NULL restores the default handler.)
  *        data: the opaque pointer to pass to fun above, must be NULL for the default handler.
  *
  *  See also haskellsecp256k1_v0_1_0_context_set_error_callback.
  */
 SECP256K1_API void haskellsecp256k1_v0_1_0_context_set_illegal_callback(
     haskellsecp256k1_v0_1_0_context *ctx,
     void (*fun)(const char *message, void *data),
     const void *data
 ) SECP256K1_ARG_NONNULL(1);
 
 /** Set a callback function to be called when an internal consistency check
  *  fails.
  *
  *  The default callback writes an error message to stderr and calls abort
  *  to abort the program.
  *
  *  This can only trigger in case of a hardware failure, miscompilation,
  *  memory corruption, serious bug in the library, or other error would can
  *  otherwise result in undefined behaviour. It will not trigger due to mere
  *  incorrect usage of the API (see haskellsecp256k1_v0_1_0_context_set_illegal_callback
  *  for that). After this callback returns, anything may happen, including
  *  crashing.
  *
  *  Args: ctx:  pointer to a context object.
  *  In:   fun:  pointer to a function to call when an internal error occurs,
  *              taking a message and an opaque pointer (NULL restores the
  *              default handler, see haskellsecp256k1_v0_1_0_context_set_illegal_callback
  *              for details).
  *        data: the opaque pointer to pass to fun above, must be NULL for the default handler.
  *
  *  See also haskellsecp256k1_v0_1_0_context_set_illegal_callback.
  */
 SECP256K1_API void haskellsecp256k1_v0_1_0_context_set_error_callback(
     haskellsecp256k1_v0_1_0_context *ctx,
     void (*fun)(const char *message, void *data),
     const void *data
 ) SECP256K1_ARG_NONNULL(1);
 
 /** Create a secp256k1 scratch space object.
  *
  *  Returns: a newly created scratch space.
  *  Args: ctx:  pointer to a context object.
  *  In:   size: amount of memory to be available as scratch space. Some extra
  *              (<100 bytes) will be allocated for extra accounting.
  */
 SECP256K1_API SECP256K1_WARN_UNUSED_RESULT haskellsecp256k1_v0_1_0_scratch_space *haskellsecp256k1_v0_1_0_scratch_space_create(
     const haskellsecp256k1_v0_1_0_context *ctx,
     size_t size
 ) SECP256K1_ARG_NONNULL(1);
 
 /** Destroy a secp256k1 scratch space.
  *
  *  The pointer may not be used afterwards.
  *  Args:       ctx: pointer to a context object.
  *          scratch: space to destroy
  */
 SECP256K1_API void haskellsecp256k1_v0_1_0_scratch_space_destroy(
     const haskellsecp256k1_v0_1_0_context *ctx,
     haskellsecp256k1_v0_1_0_scratch_space *scratch
 ) SECP256K1_ARG_NONNULL(1);
 
 /** Parse a variable-length public key into the pubkey object.
  *
  *  Returns: 1 if the public key was fully valid.
  *           0 if the public key could not be parsed or is invalid.
  *  Args: ctx:      pointer to a context object.
  *  Out:  pubkey:   pointer to a pubkey object. If 1 is returned, it is set to a
  *                  parsed version of input. If not, its value is undefined.
  *  In:   input:    pointer to a serialized public key
  *        inputlen: length of the array pointed to by input
  *
  *  This function supports parsing compressed (33 bytes, header byte 0x02 or
  *  0x03), uncompressed (65 bytes, header byte 0x04), or hybrid (65 bytes, header
  *  byte 0x06 or 0x07) format public keys.
  */
 SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int haskellsecp256k1_v0_1_0_ec_pubkey_parse(
     const haskellsecp256k1_v0_1_0_context *ctx,
     haskellsecp256k1_v0_1_0_pubkey *pubkey,
     const unsigned char *input,
     size_t inputlen
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
 
 /** Serialize a pubkey object into a serialized byte sequence.
  *
  *  Returns: 1 always.
  *  Args:   ctx:        pointer to a context object.
  *  Out:    output:     pointer to a 65-byte (if compressed==0) or 33-byte (if
  *                      compressed==1) byte array to place the serialized key
  *                      in.
  *  In/Out: outputlen:  pointer to an integer which is initially set to the
  *                      size of output, and is overwritten with the written
  *                      size.
  *  In:     pubkey:     pointer to a haskellsecp256k1_v0_1_0_pubkey containing an
  *                      initialized public key.
  *          flags:      SECP256K1_EC_COMPRESSED if serialization should be in
  *                      compressed format, otherwise SECP256K1_EC_UNCOMPRESSED.
  */
 SECP256K1_API int haskellsecp256k1_v0_1_0_ec_pubkey_serialize(
     const haskellsecp256k1_v0_1_0_context *ctx,
     unsigned char *output,
     size_t *outputlen,
     const haskellsecp256k1_v0_1_0_pubkey *pubkey,
     unsigned int flags
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
 
 /** Compare two public keys using lexicographic (of compressed serialization) order
  *
  *  Returns: <0 if the first public key is less than the second
  *           >0 if the first public key is greater than the second
  *           0 if the two public keys are equal
  *  Args: ctx:      pointer to a context object
  *  In:   pubkey1:  first public key to compare
  *        pubkey2:  second public key to compare
  */
 SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int haskellsecp256k1_v0_1_0_ec_pubkey_cmp(
     const haskellsecp256k1_v0_1_0_context *ctx,
     const haskellsecp256k1_v0_1_0_pubkey *pubkey1,
     const haskellsecp256k1_v0_1_0_pubkey *pubkey2
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
 
 /** Parse an ECDSA signature in compact (64 bytes) format.
  *
  *  Returns: 1 when the signature could be parsed, 0 otherwise.
  *  Args: ctx:      pointer to a context object
  *  Out:  sig:      pointer to a signature object
  *  In:   input64:  pointer to the 64-byte array to parse
  *
  *  The signature must consist of a 32-byte big endian R value, followed by a
  *  32-byte big endian S value. If R or S fall outside of [0..order-1], the
  *  encoding is invalid. R and S with value 0 are allowed in the encoding.
  *
  *  After the call, sig will always be initialized. If parsing failed or R or
  *  S are zero, the resulting sig value is guaranteed to fail verification for
  *  any message and public key.
  */
 SECP256K1_API int haskellsecp256k1_v0_1_0_ecdsa_signature_parse_compact(
     const haskellsecp256k1_v0_1_0_context *ctx,
     haskellsecp256k1_v0_1_0_ecdsa_signature *sig,
     const unsigned char *input64
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
 
 /** Parse a DER ECDSA signature.
  *
  *  Returns: 1 when the signature could be parsed, 0 otherwise.
  *  Args: ctx:      pointer to a context object
  *  Out:  sig:      pointer to a signature object
  *  In:   input:    pointer to the signature to be parsed
  *        inputlen: the length of the array pointed to be input
  *
  *  This function will accept any valid DER encoded signature, even if the
  *  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 haskellsecp256k1_v0_1_0_ecdsa_signature_parse_der(
     const haskellsecp256k1_v0_1_0_context *ctx,
     haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_ecdsa_signature_serialize_der(
     const haskellsecp256k1_v0_1_0_context *ctx,
     unsigned char *output,
     size_t *outputlen,
     const haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_ecdsa_signature_parse_compact for details about the encoding.
  */
 SECP256K1_API int haskellsecp256k1_v0_1_0_ecdsa_signature_serialize_compact(
     const haskellsecp256k1_v0_1_0_context *ctx,
     unsigned char *output64,
     const haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_ecdsa_verify(
     const haskellsecp256k1_v0_1_0_context *ctx,
     const haskellsecp256k1_v0_1_0_ecdsa_signature *sig,
     const unsigned char *msghash32,
     const haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_ecdsa_sign function will by default create signatures in the
  *  lower-S form, and haskellsecp256k1_v0_1_0_ecdsa_verify will not accept others. In case
  *  signatures come from a system that cannot enforce this property,
  *  haskellsecp256k1_v0_1_0_ecdsa_signature_normalize must be called before verification.
  */
 SECP256K1_API int haskellsecp256k1_v0_1_0_ecdsa_signature_normalize(
     const haskellsecp256k1_v0_1_0_context *ctx,
     haskellsecp256k1_v0_1_0_ecdsa_signature *sigout,
     const haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_nonce_function haskellsecp256k1_v0_1_0_nonce_function_rfc6979;
 
 /** A default safe nonce generation function (currently equal to haskellsecp256k1_v0_1_0_nonce_function_rfc6979). */
 SECP256K1_API const haskellsecp256k1_v0_1_0_nonce_function haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_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,
  *                      haskellsecp256k1_v0_1_0_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
  *                      haskellsecp256k1_v0_1_0_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
  * haskellsecp256k1_v0_1_0_ecdsa_signature_normalize for more details.
  */
 SECP256K1_API int haskellsecp256k1_v0_1_0_ecdsa_sign(
     const haskellsecp256k1_v0_1_0_context *ctx,
     haskellsecp256k1_v0_1_0_ecdsa_signature *sig,
     const unsigned char *msghash32,
     const unsigned char *seckey,
     haskellsecp256k1_v0_1_0_nonce_function noncefp,
     const void *ndata
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
 
 /** Verify an ECDSA 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.
  *
  *  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 haskellsecp256k1_v0_1_0_ec_seckey_verify(
     const haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_ec_pubkey_create(
     const haskellsecp256k1_v0_1_0_context *ctx,
     haskellsecp256k1_v0_1_0_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
  *           haskellsecp256k1_v0_1_0_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
  *                  haskellsecp256k1_v0_1_0_ec_seckey_verify, this function returns 0 and
  *                  seckey will be set to some unspecified value.
  */
 SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int haskellsecp256k1_v0_1_0_ec_seckey_negate(
     const haskellsecp256k1_v0_1_0_context *ctx,
     unsigned char *seckey
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
 
 /** Same as haskellsecp256k1_v0_1_0_ec_seckey_negate, but DEPRECATED. Will be removed in
  *  future versions. */
 SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int haskellsecp256k1_v0_1_0_ec_privkey_negate(
     const haskellsecp256k1_v0_1_0_context *ctx,
     unsigned char *seckey
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2)
   SECP256K1_DEPRECATED("Use haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_ec_pubkey_negate(
     const haskellsecp256k1_v0_1_0_context *ctx,
     haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_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
  *                  haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_ec_seckey_tweak_add(
     const haskellsecp256k1_v0_1_0_context *ctx,
     unsigned char *seckey,
     const unsigned char *tweak32
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
 
 /** Same as haskellsecp256k1_v0_1_0_ec_seckey_tweak_add, but DEPRECATED. Will be removed in
  *  future versions. */
 SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int haskellsecp256k1_v0_1_0_ec_privkey_tweak_add(
     const haskellsecp256k1_v0_1_0_context *ctx,
     unsigned char *seckey,
     const unsigned char *tweak32
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3)
   SECP256K1_DEPRECATED("Use haskellsecp256k1_v0_1_0_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
  *                  haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_ec_pubkey_tweak_add(
     const haskellsecp256k1_v0_1_0_context *ctx,
     haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_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
  *                  haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_ec_seckey_tweak_mul(
     const haskellsecp256k1_v0_1_0_context *ctx,
     unsigned char *seckey,
     const unsigned char *tweak32
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
 
 /** Same as haskellsecp256k1_v0_1_0_ec_seckey_tweak_mul, but DEPRECATED. Will be removed in
  *  future versions. */
 SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int haskellsecp256k1_v0_1_0_ec_privkey_tweak_mul(
     const haskellsecp256k1_v0_1_0_context *ctx,
     unsigned char *seckey,
     const unsigned char *tweak32
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3)
   SECP256K1_DEPRECATED("Use haskellsecp256k1_v0_1_0_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
  *                  haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_ec_pubkey_tweak_mul(
     const haskellsecp256k1_v0_1_0_context *ctx,
     haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_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
  * haskellsecp256k1_v0_1_0_context_create or haskellsecp256k1_v0_1_0_context_clone (or from the corresponding
  * functions in haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_context_randomize(
     haskellsecp256k1_v0_1_0_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 haskellsecp256k1_v0_1_0_ec_pubkey_combine(
     const haskellsecp256k1_v0_1_0_context *ctx,
     haskellsecp256k1_v0_1_0_pubkey *out,
     const haskellsecp256k1_v0_1_0_pubkey * const *ins,
     size_t n
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
 
 /** Compute a tagged hash as defined in BIP-340.
  *
  *  This is useful for creating a message hash and achieving domain separation
  *  through an application-specific tag. This function returns
  *  SHA256(SHA256(tag)||SHA256(tag)||msg). Therefore, tagged hash
  *  implementations optimized for a specific tag can precompute the SHA256 state
  *  after hashing the tag hashes.
  *
  *  Returns: 1 always.
  *  Args:    ctx: pointer to a context object
  *  Out:  hash32: pointer to a 32-byte array to store the resulting hash
  *  In:      tag: pointer to an array containing the tag
  *        taglen: length of the tag array
  *           msg: pointer to an array containing the message
  *        msglen: length of the message array
  */
 SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int haskellsecp256k1_v0_1_0_tagged_sha256(
     const haskellsecp256k1_v0_1_0_context *ctx,
     unsigned char *hash32,
     const unsigned char *tag,
     size_t taglen,
     const unsigned char *msg,
     size_t msglen
 ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(5);
 
 #ifdef __cplusplus
 }
 #endif
 
 #endif /* SECP256K1_H */