text: #ifndef _SECP256K1_
  # define _SECP256K1_
  
  # ifdef __cplusplus
  extern "C" {
  # endif
  
  #include <stddef.h>
  
  /* These 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 the 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, private 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 (precomputed tables etc.).
   *
   *  The purpose of context structures is to cache large precomputed data tables
   *  that are expensive to construct, and also to maintain the randomization data
   *  for blinding.
   *
   *  Do not create a new context object for each operation, as construction is
   *  far slower than all other API calls (~100 times slower than an ECDSA
   *  verification).
   *
   *  A constructed context can safely be used from multiple threads
   *  simultaneously, but API call that take a non-const pointer to a context
   *  need exclusive access to it. In particular this is the case for
   *  secp256k1_context_destroy and secp256k1_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 secp256k1_context_struct secp256k1_context;
  
  /** 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
   *  secp256k1_ec_pubkey_serialize and secp256k1_ec_pubkey_parse.
   *
   *  Furthermore, it is guaranteed that identical public keys (ignoring
   *  compression) will have identical representation, so they can be memcmp'ed.
   */
  typedef struct
  {
  	unsigned char data[64];
  }secp256k1_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 or transmission, use
   *  the secp256k1_ecdsa_signature_serialize_* and
   *  secp256k1_ecdsa_signature_serialize_* functions.
   *
   *  Furthermore, it is guaranteed to identical signatures will have identical
   *  representation, so they can be memcmp'ed.
   */
  typedef struct
  {
  	unsigned char data[64];
  }secp256k1_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 (*secp256k1_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
  
  # if (!defined(__STDC_VERSION__) || (__STDC_VERSION__ < 199901L) )
  #  if SECP256K1_GNUC_PREREQ(2,7)
  #   define SECP256K1_INLINE __inline__
  #  elif (defined(_MSC_VER))
  #   define SECP256K1_INLINE __inline
  #  else
  #   define SECP256K1_INLINE
  #  endif
  # else
  #  define SECP256K1_INLINE inline
  # endif
  
  #ifndef SECP256K1_API
  # if defined(_WIN32)
  #  ifdef SECP256K1_BUILD
  #   define SECP256K1_API __declspec(dllexport)
  #  else
  #   define SECP256K1_API
  #  endif
  # elif defined(__GNUC__) && defined(SECP256K1_BUILD)
  #  define SECP256K1_API __attribute__ ((visibility ("default")))
  # else
  #  define SECP256K1_API
  # 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
  
  /** 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_COMPRESSION (1 << 8)
  
  /** Flags to pass to secp256k1_context_create. */
  #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)
  #define SECP256K1_CONTEXT_NONE (SECP256K1_FLAGS_TYPE_CONTEXT)
  
  /** Flag to pass to secp256k1_ec_pubkey_serialize and secp256k1_ec_privkey_export. */
  #define SECP256K1_EC_COMPRESSED (SECP256K1_FLAGS_TYPE_COMPRESSION | SECP256K1_FLAGS_BIT_COMPRESSION)
  #define SECP256K1_EC_UNCOMPRESSED (SECP256K1_FLAGS_TYPE_COMPRESSION)
  
  /** Create a secp256k1 context object.
   *
   *  Returns: a newly created context object.
   *  In:      flags: which parts of the context to initialize.
   */
  SECP256K1_API secp256k1_context *secp256k1_context_create(unsigned int flags) SECP256K1_WARN_UNUSED_RESULT;
  
  /** Copies a secp256k1 context object.
   *
   *  Returns: a newly created context object.
   *  Args:    ctx: an existing context to copy (cannot be NULL)
   */
  SECP256K1_API secp256k1_context *secp256k1_context_clone(const secp256k1_context *ctx) SECP256K1_ARG_NONNULL(1) SECP256K1_WARN_UNUSED_RESULT;
  
  /** Destroy a secp256k1 context object.
   *
   *  The context pointer may not be used afterwards.
   *  Args:   ctx: an existing context to destroy (cannot be NULL)
   */
  SECP256K1_API void secp256k1_context_destroy(secp256k1_context *ctx);
  
  /** 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.
   *
   *  Args: ctx:  an existing context object (cannot be NULL)
   *  In:   fun:  a pointer to a function to call when an illegal argument is
   *              passed to the API, taking a message and an opaque pointer
   *              (NULL restores a default handler that calls abort).
   *        data: the opaque pointer to pass to fun above.
   */
  SECP256K1_API void secp256k1_context_set_illegal_callback(secp256k1_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 is crashing.
   *
   *  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 secp256k1_context_set_illegal_callback
   *  for that). After this callback returns, anything may happen, including
   *  crashing.
   *
   *  Args: ctx:  an existing context object (cannot be NULL)
   *  In:   fun:  a pointer to a function to call when an internal error occurs,
   *              taking a message and an opaque pointer (NULL restores a default
   *              handler that calls abort).
   *        data: the opaque pointer to pass to fun above.
   */
  SECP256K1_API void secp256k1_context_set_error_callback(secp256k1_context *ctx, void (*fun)(const char *message, void *data), const void *data) 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:      a secp256k1 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 secp256k1_ec_pubkey_parse(const secp256k1_context *ctx, secp256k1_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:        a secp256k1 context object.
   *  Out:    output:     a 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:  a pointer to an integer which is initially set to the
   *                      size of output, and is overwritten with the written
   *                      size.
   *  In:     pubkey:     a pointer to a secp256k1_pubkey containing an
   *                      initialized public key.
   *          flags:      SECP256K1_EC_COMPRESSED if serialization should be in
   *                      compressed format, otherwise SECP256K1_EC_UNCOMPRESSED.
   */
  SECP256K1_API int secp256k1_ec_pubkey_serialize(const secp256k1_context *ctx, unsigned char *output, size_t *outputlen, const secp256k1_pubkey *pubkey, unsigned int flags) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
  
  /** Parse an ECDSA signature in compact (64 bytes) format.
   *
   *  Returns: 1 when the signature could be parsed, 0 otherwise.
   *  Args: ctx:      a secp256k1 context object
   *  Out:  sig:      a pointer to a signature object
   *  In:   input64:  a 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 validation for any
   *  message and public key.
   */
  SECP256K1_API int secp256k1_ecdsa_signature_parse_compact(const secp256k1_context *ctx, secp256k1_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:      a secp256k1 context object
   *  Out:  sig:      a pointer to a signature object
   *  In:   input:    a 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 validation with it is
   *  guaranteed to fail for every message and public key.
   */
  SECP256K1_API int secp256k1_ecdsa_signature_parse_der(const secp256k1_context *ctx, secp256k1_ecdsa_signature *sig, const unsigned char *input, size_t inputlen) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
  
  /** Serialize an ECDSA signature in DER format.
   *
   *  Returns: 1 if enough space was available to serialize, 0 otherwise
   *  Args:   ctx:       a secp256k1 context object
   *  Out:    output:    a pointer to an array to store the DER serialization
   *  In/Out: outputlen: a 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:       a pointer to an initialized signature object
   */
  SECP256K1_API int secp256k1_ecdsa_signature_serialize_der(const secp256k1_context *ctx, unsigned char *output, size_t *outputlen, const secp256k1_ecdsa_signature *sig) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
  
  /** Serialize an ECDSA signature in compact (64 byte) format.
   *
   *  Returns: 1
   *  Args:   ctx:       a secp256k1 context object
   *  Out:    output64:  a pointer to a 64-byte array to store the compact serialization
   *  In:     sig:       a pointer to an initialized signature object
   *
   *  See secp256k1_ecdsa_signature_parse_compact for details about the encoding.
   */
  SECP256K1_API int secp256k1_ecdsa_signature_serialize_compact(const secp256k1_context *ctx, unsigned char *output64, const secp256k1_ecdsa_signature *sig) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
  
  /** Verify an ECDSA signature.
   *
   *  Returns: 1: correct signature
   *           0: incorrect or unparseable signature
   *  Args:    ctx:       a secp256k1 context object, initialized for verification.
   *  In:      sig:       the signature being verified (cannot be NULL)
   *           msg32:     the 32-byte message hash being verified (cannot be NULL)
   *           pubkey:    pointer to an initialized public key to verify with (cannot be NULL)
   *
   * To avoid accepting malleable signatures, only ECDSA signatures in lower-S
   * form are accepted.
   *
   * If you need to accept ECDSA signatures from sources that do not obey this
   * rule, apply secp256k1_ecdsa_signature_normalize to the signature prior to
   * validation, but be aware that doing so results in malleable signatures.
   *
   * For details, see the comments for that function.
   */
  SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdsa_verify(const secp256k1_context *ctx, const secp256k1_ecdsa_signature *sig, const unsigned char *msg32, const secp256k1_pubkey *pubkey) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
  
  /** Convert a signature to a normalized lower-S form.
   *
   *  Returns: 1 if sigin was not normalized, 0 if it already was.
   *  Args: ctx:    a secp256k1 context object
   *  Out:  sigout: a 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:  a pointer to a signature to check/normalize (cannot be NULL,
   *                can be identical to sigout)
   *
   *  With ECDSA a third-party can forge a second distinct signature of the same
   *  message, given a single initial signature, but without knowing the key. This
   *  is done by negating the S value modulo the order of the curve, 'flipping'
   *  the sign of the random point R which is not included in the signature.
   *
   *  Forgery of the same message isn't universally problematic, but in systems
   *  where message malleability or uniqueness of signatures is important this can
   *  cause issues. This forgery can be blocked by all verifiers forcing signers
   *  to use a normalized form.
   *
   *  The lower-S form reduces the size of signatures slightly on average when
   *  variable length encodings (such as DER) are used and is cheap to verify,
   *  making it a good choice. Security of always using lower-S is assured because
   *  anyone can trivially modify a signature after the fact to enforce this
   *  property anyway.
   *
   *  The lower S value is always between 0x1 and
   *  0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0,
   *  inclusive.
   *
   *  No other forms of ECDSA malleability are known and none seem likely, but
   *  there is no formal proof that ECDSA, even with this additional restriction,
   *  is free of other malleability. Commonly used serialization schemes will also
   *  accept various non-unique encodings, so care should be taken when this
   *  property is required for an application.
   *
   *  The secp256k1_ecdsa_sign function will by default create signatures in the
   *  lower-S form, and secp256k1_ecdsa_verify will not accept others. In case
   *  signatures come from a system that cannot enforce this property,
   *  secp256k1_ecdsa_signature_normalize must be called before verification.
   */
  SECP256K1_API int secp256k1_ecdsa_signature_normalize(const secp256k1_context *ctx, secp256k1_ecdsa_signature *sigout, const secp256k1_ecdsa_signature *sigin) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(3);
  
  /** An implementation of RFC6979 (using HMAC-SHA256) as nonce generation function.
   * If a data pointer is passed, it is assumed to be a pointer to 32 bytes of
   * extra entropy.
   */
  SECP256K1_API extern const secp256k1_nonce_function secp256k1_nonce_function_rfc6979;
  
  /** A default safe nonce generation function (currently equal to secp256k1_nonce_function_rfc6979). */
  SECP256K1_API extern const secp256k1_nonce_function secp256k1_nonce_function_default;
  
  /** Create an ECDSA signature.
   *
   *  Returns: 1: signature created
   *           0: the nonce generation function failed, or the private key was invalid.
   *  Args:    ctx:    pointer to a context object, initialized for signing (cannot be NULL)
   *  Out:     sig:    pointer to an array where the signature will be placed (cannot be NULL)
   *  In:      msg32:  the 32-byte message hash being signed (cannot be NULL)
   *           seckey: pointer to a 32-byte secret key (cannot be NULL)
   *           noncefp:pointer to a nonce generation function. If NULL, secp256k1_nonce_function_default is used
   *           ndata:  pointer to arbitrary data used by the nonce generation function (can be NULL)
   *
   * The created signature is always in lower-S form. See
   * secp256k1_ecdsa_signature_normalize for more details.
   */
  SECP256K1_API int secp256k1_ecdsa_sign(const secp256k1_context *ctx, secp256k1_ecdsa_signature *sig, const unsigned char *msg32, const unsigned char *seckey, secp256k1_nonce_function noncefp, const void *ndata) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
  
  /** Verify an ECDSA secret key.
   *
   *  Returns: 1: secret key is valid
   *           0: secret key is invalid
   *  Args:    ctx: pointer to a context object (cannot be NULL)
   *  In:      seckey: pointer to a 32-byte secret key (cannot be NULL)
   */
  SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_verify(const secp256k1_context *ctx, const unsigned char *seckey) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
  
  /** Compute the public key for a secret key.
   *
   *  Returns: 1: secret was valid, public key stores
   *           0: secret was invalid, try again
   *  Args:   ctx:        pointer to a context object, initialized for signing (cannot be NULL)
   *  Out:    pubkey:     pointer to the created public key (cannot be NULL)
   *  In:     seckey:     pointer to a 32-byte private key (cannot be NULL)
   */
  SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_create(const secp256k1_context *ctx, secp256k1_pubkey *pubkey, const unsigned char *seckey) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
  
  /** Tweak a private key by adding tweak to it.
   * Returns: 0 if the tweak was out of range (chance of around 1 in 2^128 for
   *          uniformly random 32-byte arrays, or if the resulting private key
   *          would be invalid (only when the tweak is the complement of the
   *          private key). 1 otherwise.
   * Args:    ctx:    pointer to a context object (cannot be NULL).
   * In/Out:  seckey: pointer to a 32-byte private key.
   * In:      tweak:  pointer to a 32-byte tweak.
   */
  SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_add(const secp256k1_context *ctx, unsigned char *seckey, const unsigned char *tweak) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
  
  /** Tweak a public key by adding tweak times the generator to it.
   * Returns: 0 if the tweak was out of range (chance of around 1 in 2^128 for
   *          uniformly random 32-byte arrays, or if the resulting public key
   *          would be invalid (only when the tweak is the complement of the
   *          corresponding private key). 1 otherwise.
   * Args:    ctx:    pointer to a context object initialized for validation
   *                  (cannot be NULL).
   * In/Out:  pubkey: pointer to a public key object.
   * In:      tweak:  pointer to a 32-byte tweak.
   */
  SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_add(const secp256k1_context *ctx, secp256k1_pubkey *pubkey, const unsigned char *tweak) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
  
  /** Tweak a private key by multiplying it by a tweak.
   * Returns: 0 if the tweak was out of range (chance of around 1 in 2^128 for
   *          uniformly random 32-byte arrays, or equal to zero. 1 otherwise.
   * Args:   ctx:    pointer to a context object (cannot be NULL).
   * In/Out: seckey: pointer to a 32-byte private key.
   * In:     tweak:  pointer to a 32-byte tweak.
   */
  SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_mul(const secp256k1_context *ctx, unsigned char *seckey, const unsigned char *tweak) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
  
  /** Tweak a public key by multiplying it by a tweak value.
   * Returns: 0 if the tweak was out of range (chance of around 1 in 2^128 for
   *          uniformly random 32-byte arrays, or equal to zero. 1 otherwise.
   * Args:    ctx:    pointer to a context object initialized for validation
   *                 (cannot be NULL).
   * In/Out:  pubkey: pointer to a public key obkect.
   * In:      tweak:  pointer to a 32-byte tweak.
   */
  SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_mul(const secp256k1_context *ctx, secp256k1_pubkey *pubkey, const unsigned char *tweak) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
  
  /** Updates the context randomization.
   *  Returns: 1: randomization successfully updated
   *           0: error
   *  Args:    ctx:       pointer to a context object (cannot be NULL)
   *  In:      seed32:    pointer to a 32-byte random seed (NULL resets to initial state)
   */
  SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_context_randomize(secp256k1_context *ctx, const unsigned char *seed32) SECP256K1_ARG_NONNULL(1);
  
  /** Add a number of public keys together.
   *  Returns: 1: the sum of the public keys is valid.
   *           0: the sum of the public keys is not valid.
   *  Args:   ctx:        pointer to a context object
   *  Out:    out:        pointer to a public key object for placing the resulting public key
   *                      (cannot be NULL)
   *  In:     ins:        pointer to array of pointers to public keys (cannot be NULL)
   *          n:          the number of public keys to add together (must be at least 1)
   */
  SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_combine(const secp256k1_context *ctx, secp256k1_pubkey *out, const secp256k1_pubkey * const *ins, size_t n) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
  
  # ifdef __cplusplus
  }
  # endif
  
  #endif
  