Squashed commit of the following:

commit 0a40e209d03e8ff9b6f81cd5969d3e845c633bfc
Author: vnugent <public@vaughnnugent.com>
Date:   Sat May 4 13:55:19 2024 -0400

    ci: Force disable testing for win ci builds

commit 55fae189fffc86f07a3448370f0a746670819712
Author: vnugent <public@vaughnnugent.com>
Date:   Thu May 2 21:54:35 2024 -0400

    feat: Working and tested openssl impl & defaults

commit 6ff8bb11774c51fd341b7699a3938fd894995fbf
Author: vnugent <public@vaughnnugent.com>
Date:   Thu Apr 25 17:45:42 2024 -0400

    refactor: Finish support and testing for mbedtls

commit 7cb7a93de4f6f5e741bc5129e3d928e44f050930
Author: vnugent <public@vaughnnugent.com>
Date:   Tue Apr 23 18:19:31 2024 -0400

    refactor!: MbedTLS on Windows, switch to uint32

commit 30e8dda6cbea86bdee6d5dfe48514385d3b9f81b
Author: vnugent <public@vaughnnugent.com>
Date:   Tue Apr 23 14:48:05 2024 -0400

    refactor: Crypto dep redesign working on Windows

commit d09c6c1bd5da3e2d79351daeba304ca99976a726
Author: vnugent <public@vaughnnugent.com>
Date:   Thu Apr 18 00:28:51 2024 -0400

    refactor!: Pushing what I have to dev

commit 54e06ada7d624ed0d28c6a6db04a149708841bf8
Author: vnugent <public@vaughnnugent.com>
Date:   Sat Apr 13 01:24:00 2024 -0400

    fix: convert constants to hex, inline macro, ParseErrorCode

commit 4215e3100d9a0d23119080d09638fa5b60d0c6d4
Merge: d3328f4 7485aa5
Author: vnugent <public@vaughnnugent.com>
Date:   Wed Apr 3 18:26:30 2024 -0400

    Merge branch 'master' into develop

commit d3328f4152b22b28f24c43dda62464287f1efff5
Author: vnugent <public@vaughnnugent.com>
Date:   Wed Apr 3 18:22:56 2024 -0400

    build: Included dependency and versions in client builds

commit b11bc0bac955fd5c6db65f0da48456bf5e748805
Author: vnugent <public@vaughnnugent.com>
Date:   Wed Apr 3 18:10:08 2024 -0400

    fix: Fix c89 compatabilty comments and struct assignment

commit 9915bd41799a72413e6b400e150aa9f5fa797e25
Merge: 8e3d6ea 5184d7d
Author: vnugent <public@vaughnnugent.com>
Date:   Sat Mar 30 09:57:30 2024 -0400

    Merge branch 'master' into develop

commit 8e3d6ea5e3c83fe42cb904b6ccc4fe2b73f76aae
Author: vnugent <public@vaughnnugent.com>
Date:   Sat Mar 30 09:52:55 2024 -0400

    refactor!: Some api (struct) changes and updated tests

commit e88e8420520204e20802516f01d4488bb0b1d6ea
Merge: 490dfee 21f6c0a
Author: vnugent <public@vaughnnugent.com>
Date:   Sun Mar 3 15:02:34 2024 -0500

    Merge branch 'master' into develop

commit 490dfee4ef22479009627435c6ad728c3cbbab54
Author: vnugent <public@vaughnnugent.com>
Date:   Sun Mar 3 14:59:25 2024 -0500

    test: #3 tests for encryption/description and Macs

commit efa97490b7ed47f4e2f05bee52e2b33e14e439e6
Merge: 1b84e3c 120022a
Author: vnugent <public@vaughnnugent.com>
Date:   Sun Mar 3 14:55:48 2024 -0500

    merge master

commit 1b84e3c7c2e55b1ff9ffdd09b66873e11c131441
Author: vnugent <public@vaughnnugent.com>
Date:   Sat Mar 2 22:57:36 2024 -0500

    fix: #2 constent usage of sizeof() operator on struct types

commit 9de5a214c66adea0ef2d0bac63c59449de202a88
Author: vnugent <public@vaughnnugent.com>
Date:   Fri Mar 1 14:30:36 2024 -0500

    perf: avoid nc_key struct copy, cast and verify instead

commit b917b761120ed684af28d0707673ffadcf14b8fe
Author: vnugent <public@vaughnnugent.com>
Date:   Mon Feb 12 22:06:50 2024 -0500

    fix: found the constant time memcompare function

commit 9f85fff3b9f25da7410569ea94f994b88feb3910
Author: vnugent <public@vaughnnugent.com>
Date:   Fri Feb 9 22:48:35 2024 -0500

    feat: added/update MAC functions to sign or verify nip44 payload

commit aa5113741bb419b02d6ea416bba571fa3d65db46
Author: vnugent <public@vaughnnugent.com>
Date:   Wed Feb 7 01:37:53 2024 -0500

    add missing hmac-key output buffer

commit 55f47d22cc9ce4d1e22b70814d608c7ef3b1bbc9
Author: vnugent <public@vaughnnugent.com>
Date:   Sun Feb 4 21:08:13 2024 -0500

    simple bug fixes, and public api argument validation tests

commit 73c5a713fb164ae8b4ac8a891a8020e08eae0a3b
Author: vnugent <public@vaughnnugent.com>
Date:   Fri Feb 2 23:05:48 2024 -0500

    update api to return secpvalidate return code instead of internal return codes

commit 06c73004e1a39a7ea4ea3a89c22dee0f66adb236
Author: vnugent <public@vaughnnugent.com>
Date:   Fri Feb 2 19:25:17 2024 -0500

    change to lgpl license

commit 6e79fdb3b6b6739fc7797d47e55a7691306cf736
Author: vnugent <public@vaughnnugent.com>
Date:   Wed Jan 31 21:30:49 2024 -0500

    move validation macros, and optionally disable them

commit ac1e58837f1ba687939f78b5c03cadd346c10ddd
Author: vnugent <public@vaughnnugent.com>
Date:   Tue Jan 30 12:25:05 2024 -0500

    couple more tests, renable range checks, set flags for all projects

4 files changed, 1409 insertions, 0 deletions

diff --git a/vendor/secp256k1/include/secp256k1/secp256k1.h b/vendor/secp256k1/include/secp256k1/secp256k1.h
new file mode 100644
index 0000000..f4053f2
--- /dev/null
+++ b/vendor/secp256k1/include/secp256k1/secp256k1.h
@@ -0,0 +1,909 @@
+#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
+ *  secp256k1_context_create for creation of contexts and
+ *  secp256k1_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
+ *  secp256k1_context_set_error_callback as well as
+ *  secp256k1_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
+ *  secp256k1_context_destroy, secp256k1_context_preallocated_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 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 secp256k1_scratch_space_struct secp256k1_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 secp256k1_ec_pubkey_serialize and secp256k1_ec_pubkey_parse. To
+ *  compare keys, use secp256k1_ec_pubkey_cmp.
+ */
+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, transmission, or
+ *  comparison, use the secp256k1_ecdsa_signature_serialize_* and
+ *  secp256k1_ecdsa_signature_parse_* functions.
+ */
+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
+
+/*  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 secp256k1_context_create, secp256k1_context_preallocated_size, and
+ *  secp256k1_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 secp256k1_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 secp256k1_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 secp256k1_context_create if you need a
+ *  full context object that supports all functionality offered by the library.
+ *
+ *  It is highly recommended to call secp256k1_selftest before using this context.
+ */
+SECP256K1_API const secp256k1_context *secp256k1_context_static;
+
+/** Deprecated alias for secp256k1_context_static. */
+SECP256K1_API const secp256k1_context *secp256k1_context_no_precomp
+SECP256K1_DEPRECATED("Use secp256k1_context_static instead");
+
+/** Perform basic self tests (to be used in conjunction with secp256k1_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 secp256k1_context_static.
+ *  It is not necessary to call this function before using a context created with
+ *  secp256k1_context_create (or secp256k1_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 secp256k1_context_set_error_callback).
+ */
+SECP256K1_API void secp256k1_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 secp256k1_context_static and the functions in
+ *  secp256k1_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 secp256k1_context_randomize on the context before calling
+ *  those API functions. This will provide enhanced protection against side-channel
+ *  leakage, see secp256k1_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 secp256k1_context *secp256k1_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 secp256k1_preallocated.h.
+ *
+ *  Cloning secp256k1_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 secp256k1_context_static).
+ */
+SECP256K1_API secp256k1_context *secp256k1_context_clone(
+    const secp256k1_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 secp256k1_context_create
+ *  or secp256k1_context_clone. If the context has instead been created using
+ *  secp256k1_context_preallocated_create or secp256k1_context_preallocated_clone, the
+ *  behaviour is undefined. In that case, secp256k1_context_preallocated_destroy must
+ *  be used instead.
+ *
+ *  Args:   ctx: pointer to a context to destroy, constructed using
+ *               secp256k1_context_create or secp256k1_context_clone
+ *               (i.e., not secp256k1_context_static).
+ */
+SECP256K1_API void secp256k1_context_destroy(
+    secp256k1_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 secp256k1_default_illegal_callback_fn(const char *message, void *data);
+ *   - void secp256k1_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 secp256k1_context_set_illegal_callback or
+ *  secp256k1_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 secp256k1_context_set_error_callback.
+ */
+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 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 secp256k1_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 secp256k1_context_set_illegal_callback
+ *              for details).
+ *        data: the opaque pointer to pass to fun above, must be NULL for the default handler.
+ *
+ *  See also secp256k1_context_set_illegal_callback.
+ */
+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);
+
+/** 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 secp256k1_scratch_space *secp256k1_scratch_space_create(
+    const secp256k1_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 secp256k1_scratch_space_destroy(
+    const secp256k1_context *ctx,
+    secp256k1_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 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:        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 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);
+
+/** 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 secp256k1_ec_pubkey_cmp(
+    const secp256k1_context *ctx,
+    const secp256k1_pubkey *pubkey1,
+    const secp256k1_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 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:      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 secp256k1_ecdsa_signature_parse_der(
+    const secp256k1_context *ctx,
+    secp256k1_ecdsa_signature *sig,
+    const unsigned char *input,
+    size_t inputlen
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Serialize an ECDSA signature in DER format.
+ *
+ *  Returns: 1 if enough space was available to serialize, 0 otherwise
+ *  Args:   ctx:       pointer to a context object
+ *  Out:    output:    pointer to an array to store the DER serialization
+ *  In/Out: outputlen: pointer to a length integer. Initially, this integer
+ *                     should be set to the length of output. After the call
+ *                     it will be set to the length of the serialization (even
+ *                     if 0 was returned).
+ *  In:     sig:       pointer to an initialized signature object
+ */
+SECP256K1_API int secp256k1_ecdsa_signature_serialize_der(
+    const secp256k1_context *ctx,
+    unsigned char *output,
+    size_t *outputlen,
+    const secp256k1_ecdsa_signature *sig
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+/** Serialize an ECDSA signature in compact (64 byte) format.
+ *
+ *  Returns: 1
+ *  Args:   ctx:       pointer to a context object
+ *  Out:    output64:  pointer to a 64-byte array to store the compact serialization
+ *  In:     sig:       pointer to an initialized signature object
+ *
+ *  See secp256k1_ecdsa_signature_parse_compact for details about the encoding.
+ */
+SECP256K1_API int secp256k1_ecdsa_signature_serialize_compact(
+    const secp256k1_context *ctx,
+    unsigned char *output64,
+    const secp256k1_ecdsa_signature *sig
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Verify an ECDSA signature.
+ *
+ *  Returns: 1: correct signature
+ *           0: incorrect or unparseable signature
+ *  Args:    ctx:       pointer to a context object
+ *  In:      sig:       the signature being verified.
+ *           msghash32: the 32-byte message hash being verified.
+ *                      The verifier must make sure to apply a cryptographic
+ *                      hash function to the message by itself and not accept an
+ *                      msghash32 value directly. Otherwise, it would be easy to
+ *                      create a "valid" signature without knowledge of the
+ *                      secret key. See also
+ *                      https://bitcoin.stackexchange.com/a/81116/35586 for more
+ *                      background on this topic.
+ *           pubkey:    pointer to an initialized public key to verify with.
+ *
+ * To avoid accepting malleable signatures, only ECDSA signatures in lower-S
+ * form are accepted.
+ *
+ * If you need to accept ECDSA signatures from sources that do not obey this
+ * rule, apply secp256k1_ecdsa_signature_normalize to the signature prior to
+ * verification, but be aware that doing so results in malleable signatures.
+ *
+ * For details, see the comments for that function.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdsa_verify(
+    const secp256k1_context *ctx,
+    const secp256k1_ecdsa_signature *sig,
+    const unsigned char *msghash32,
+    const secp256k1_pubkey *pubkey
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+/** Convert a signature to a normalized lower-S form.
+ *
+ *  Returns: 1 if sigin was not normalized, 0 if it already was.
+ *  Args: ctx:    pointer to a context object
+ *  Out:  sigout: pointer to a signature to fill with the normalized form,
+ *                or copy if the input was already normalized. (can be NULL if
+ *                you're only interested in whether the input was already
+ *                normalized).
+ *  In:   sigin:  pointer to a signature to check/normalize (can be identical to sigout)
+ *
+ *  With ECDSA a third-party can forge a second distinct signature of the same
+ *  message, given a single initial signature, but without knowing the key. This
+ *  is done by negating the S value modulo the order of the curve, 'flipping'
+ *  the sign of the random point R which is not included in the signature.
+ *
+ *  Forgery of the same message isn't universally problematic, but in systems
+ *  where message malleability or uniqueness of signatures is important this can
+ *  cause issues. This forgery can be blocked by all verifiers forcing signers
+ *  to use a normalized form.
+ *
+ *  The lower-S form reduces the size of signatures slightly on average when
+ *  variable length encodings (such as DER) are used and is cheap to verify,
+ *  making it a good choice. Security of always using lower-S is assured because
+ *  anyone can trivially modify a signature after the fact to enforce this
+ *  property anyway.
+ *
+ *  The lower S value is always between 0x1 and
+ *  0x7FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF5D576E7357A4501DDFE92F46681B20A0,
+ *  inclusive.
+ *
+ *  No other forms of ECDSA malleability are known and none seem likely, but
+ *  there is no formal proof that ECDSA, even with this additional restriction,
+ *  is free of other malleability. Commonly used serialization schemes will also
+ *  accept various non-unique encodings, so care should be taken when this
+ *  property is required for an application.
+ *
+ *  The secp256k1_ecdsa_sign function will by default create signatures in the
+ *  lower-S form, and secp256k1_ecdsa_verify will not accept others. In case
+ *  signatures come from a system that cannot enforce this property,
+ *  secp256k1_ecdsa_signature_normalize must be called before verification.
+ */
+SECP256K1_API int secp256k1_ecdsa_signature_normalize(
+    const secp256k1_context *ctx,
+    secp256k1_ecdsa_signature *sigout,
+    const secp256k1_ecdsa_signature *sigin
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(3);
+
+/** An implementation of RFC6979 (using HMAC-SHA256) as nonce generation function.
+ * If a data pointer is passed, it is assumed to be a pointer to 32 bytes of
+ * extra entropy.
+ */
+SECP256K1_API const secp256k1_nonce_function secp256k1_nonce_function_rfc6979;
+
+/** A default safe nonce generation function (currently equal to secp256k1_nonce_function_rfc6979). */
+SECP256K1_API const secp256k1_nonce_function secp256k1_nonce_function_default;
+
+/** Create an ECDSA signature.
+ *
+ *  Returns: 1: signature created
+ *           0: the nonce generation function failed, or the secret key was invalid.
+ *  Args:    ctx:       pointer to a context object (not secp256k1_context_static).
+ *  Out:     sig:       pointer to an array where the signature will be placed.
+ *  In:      msghash32: the 32-byte message hash being signed.
+ *           seckey:    pointer to a 32-byte secret key.
+ *           noncefp:   pointer to a nonce generation function. If NULL,
+ *                      secp256k1_nonce_function_default is used.
+ *           ndata:     pointer to arbitrary data used by the nonce generation function
+ *                      (can be NULL). If it is non-NULL and
+ *                      secp256k1_nonce_function_default is used, then ndata must be a
+ *                      pointer to 32-bytes of additional data.
+ *
+ * The created signature is always in lower-S form. See
+ * secp256k1_ecdsa_signature_normalize for more details.
+ */
+SECP256K1_API int secp256k1_ecdsa_sign(
+    const secp256k1_context *ctx,
+    secp256k1_ecdsa_signature *sig,
+    const unsigned char *msghash32,
+    const unsigned char *seckey,
+    secp256k1_nonce_function noncefp,
+    const void *ndata
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+/** Verify an 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 secp256k1_ec_seckey_verify(
+    const secp256k1_context *ctx,
+    const unsigned char *seckey
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
+
+/** Compute the public key for a secret key.
+ *
+ *  Returns: 1: secret was valid, public key stores.
+ *           0: secret was invalid, try again.
+ *  Args:    ctx:    pointer to a context object (not secp256k1_context_static).
+ *  Out:     pubkey: pointer to the created public key.
+ *  In:      seckey: pointer to a 32-byte secret key.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_create(
+    const secp256k1_context *ctx,
+    secp256k1_pubkey *pubkey,
+    const unsigned char *seckey
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Negates a secret key in place.
+ *
+ *  Returns: 0 if the given secret key is invalid according to
+ *           secp256k1_ec_seckey_verify. 1 otherwise
+ *  Args:   ctx:    pointer to a context object
+ *  In/Out: seckey: pointer to the 32-byte secret key to be negated. If the
+ *                  secret key is invalid according to
+ *                  secp256k1_ec_seckey_verify, this function returns 0 and
+ *                  seckey will be set to some unspecified value.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_negate(
+    const secp256k1_context *ctx,
+    unsigned char *seckey
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
+
+/** Same as secp256k1_ec_seckey_negate, but DEPRECATED. Will be removed in
+ *  future versions. */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_negate(
+    const secp256k1_context *ctx,
+    unsigned char *seckey
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2)
+  SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_negate instead");
+
+/** Negates a public key in place.
+ *
+ *  Returns: 1 always
+ *  Args:   ctx:        pointer to a context object
+ *  In/Out: pubkey:     pointer to the public key to be negated.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_negate(
+    const secp256k1_context *ctx,
+    secp256k1_pubkey *pubkey
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2);
+
+/** Tweak a secret key by adding tweak to it.
+ *
+ *  Returns: 0 if the arguments are invalid or the resulting secret key would be
+ *           invalid (only when the tweak is the negation of the secret key). 1
+ *           otherwise.
+ *  Args:    ctx:   pointer to a context object.
+ *  In/Out: seckey: pointer to a 32-byte secret key. If the secret key is
+ *                  invalid according to secp256k1_ec_seckey_verify, this
+ *                  function returns 0. seckey will be set to some unspecified
+ *                  value if this function returns 0.
+ *  In:    tweak32: pointer to a 32-byte tweak, which must be valid according to
+ *                  secp256k1_ec_seckey_verify or 32 zero bytes. For uniformly
+ *                  random 32-byte tweaks, the chance of being invalid is
+ *                  negligible (around 1 in 2^128).
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_tweak_add(
+    const secp256k1_context *ctx,
+    unsigned char *seckey,
+    const unsigned char *tweak32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Same as secp256k1_ec_seckey_tweak_add, but DEPRECATED. Will be removed in
+ *  future versions. */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_add(
+    const secp256k1_context *ctx,
+    unsigned char *seckey,
+    const unsigned char *tweak32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3)
+  SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_tweak_add instead");
+
+/** Tweak a public key by adding tweak times the generator to it.
+ *
+ *  Returns: 0 if the arguments are invalid or the resulting public key would be
+ *           invalid (only when the tweak is the negation of the corresponding
+ *           secret key). 1 otherwise.
+ *  Args:    ctx:   pointer to a context object.
+ *  In/Out: pubkey: pointer to a public key object. pubkey will be set to an
+ *                  invalid value if this function returns 0.
+ *  In:    tweak32: pointer to a 32-byte tweak, which must be valid according to
+ *                  secp256k1_ec_seckey_verify or 32 zero bytes. For uniformly
+ *                  random 32-byte tweaks, the chance of being invalid is
+ *                  negligible (around 1 in 2^128).
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_add(
+    const secp256k1_context *ctx,
+    secp256k1_pubkey *pubkey,
+    const unsigned char *tweak32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Tweak a secret key by multiplying it by a tweak.
+ *
+ *  Returns: 0 if the arguments are invalid. 1 otherwise.
+ *  Args:   ctx:    pointer to a context object.
+ *  In/Out: seckey: pointer to a 32-byte secret key. If the secret key is
+ *                  invalid according to secp256k1_ec_seckey_verify, this
+ *                  function returns 0. seckey will be set to some unspecified
+ *                  value if this function returns 0.
+ *  In:    tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to
+ *                  secp256k1_ec_seckey_verify, this function returns 0. For
+ *                  uniformly random 32-byte arrays the chance of being invalid
+ *                  is negligible (around 1 in 2^128).
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_seckey_tweak_mul(
+    const secp256k1_context *ctx,
+    unsigned char *seckey,
+    const unsigned char *tweak32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Same as secp256k1_ec_seckey_tweak_mul, but DEPRECATED. Will be removed in
+ *  future versions. */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_privkey_tweak_mul(
+    const secp256k1_context *ctx,
+    unsigned char *seckey,
+    const unsigned char *tweak32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3)
+  SECP256K1_DEPRECATED("Use secp256k1_ec_seckey_tweak_mul instead");
+
+/** Tweak a public key by multiplying it by a tweak value.
+ *
+ *  Returns: 0 if the arguments are invalid. 1 otherwise.
+ *  Args:    ctx:   pointer to a context object.
+ *  In/Out: pubkey: pointer to a public key object. pubkey will be set to an
+ *                  invalid value if this function returns 0.
+ *  In:    tweak32: pointer to a 32-byte tweak. If the tweak is invalid according to
+ *                  secp256k1_ec_seckey_verify, this function returns 0. For
+ *                  uniformly random 32-byte arrays the chance of being invalid
+ *                  is negligible (around 1 in 2^128).
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_tweak_mul(
+    const secp256k1_context *ctx,
+    secp256k1_pubkey *pubkey,
+    const unsigned char *tweak32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Randomizes the context to provide enhanced protection against side-channel leakage.
+ *
+ *  Returns: 1: randomization successful
+ *           0: error
+ *  Args:    ctx:       pointer to a context object (not secp256k1_context_static).
+ *  In:      seed32:    pointer to a 32-byte random seed (NULL resets to initial state).
+ *
+ * While secp256k1 code is written and tested to be constant-time no matter what
+ * secret values are, it is possible that a compiler may output code which is not,
+ * and also that the CPU may not emit the same radio frequencies or draw the same
+ * amount of power for all values. Randomization of the context shields against
+ * side-channel observations which aim to exploit secret-dependent behaviour in
+ * certain computations which involve secret keys.
+ *
+ * It is highly recommended to call this function on contexts returned from
+ * secp256k1_context_create or secp256k1_context_clone (or from the corresponding
+ * functions in secp256k1_preallocated.h) before using these contexts to call API
+ * functions that perform computations involving secret keys, e.g., signing and
+ * public key generation. It is possible to call this function more than once on
+ * the same context, and doing so before every few computations involving secret
+ * keys is recommended as a defense-in-depth measure. Randomization of the static
+ * context secp256k1_context_static is not supported.
+ *
+ * Currently, the random seed is mainly used for blinding multiplications of a
+ * secret scalar with the elliptic curve base point. Multiplications of this
+ * kind are performed by exactly those API functions which are documented to
+ * require a context that is not secp256k1_context_static. As a rule of thumb,
+ * these are all functions which take a secret key (or a keypair) as an input.
+ * A notable exception to that rule is the ECDH module, which relies on a different
+ * kind of elliptic curve point multiplication and thus does not benefit from
+ * enhanced protection against side-channel leakage currently.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_context_randomize(
+    secp256k1_context *ctx,
+    const unsigned char *seed32
+) SECP256K1_ARG_NONNULL(1);
+
+/** Add a number of public keys together.
+ *
+ *  Returns: 1: the sum of the public keys is valid.
+ *           0: the sum of the public keys is not valid.
+ *  Args:   ctx:        pointer to a context object.
+ *  Out:    out:        pointer to a public key object for placing the resulting public key.
+ *  In:     ins:        pointer to array of pointers to public keys.
+ *          n:          the number of public keys to add together (must be at least 1).
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ec_pubkey_combine(
+    const secp256k1_context *ctx,
+    secp256k1_pubkey *out,
+    const secp256k1_pubkey * const *ins,
+    size_t n
+) 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 secp256k1_tagged_sha256(
+    const secp256k1_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 */
diff --git a/vendor/secp256k1/include/secp256k1/secp256k1_ecdh.h b/vendor/secp256k1/include/secp256k1/secp256k1_ecdh.h
new file mode 100644
index 0000000..4d9da34
--- /dev/null
+++ b/vendor/secp256k1/include/secp256k1/secp256k1_ecdh.h
@@ -0,0 +1,63 @@
+#ifndef SECP256K1_ECDH_H
+#define SECP256K1_ECDH_H
+
+#include "secp256k1.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** A pointer to a function that hashes an EC point to obtain an ECDH secret
+ *
+ *  Returns: 1 if the point was successfully hashed.
+ *           0 will cause secp256k1_ecdh to fail and return 0.
+ *           Other return values are not allowed, and the behaviour of
+ *           secp256k1_ecdh is undefined for other return values.
+ *  Out:     output:     pointer to an array to be filled by the function
+ *  In:      x32:        pointer to a 32-byte x coordinate
+ *           y32:        pointer to a 32-byte y coordinate
+ *           data:       arbitrary data pointer that is passed through
+ */
+typedef int (*secp256k1_ecdh_hash_function)(
+  unsigned char *output,
+  const unsigned char *x32,
+  const unsigned char *y32,
+  void *data
+);
+
+/** An implementation of SHA256 hash function that applies to compressed public key.
+ * Populates the output parameter with 32 bytes. */
+SECP256K1_API const secp256k1_ecdh_hash_function secp256k1_ecdh_hash_function_sha256;
+
+/** A default ECDH hash function (currently equal to secp256k1_ecdh_hash_function_sha256).
+ * Populates the output parameter with 32 bytes. */
+SECP256K1_API const secp256k1_ecdh_hash_function secp256k1_ecdh_hash_function_default;
+
+/** Compute an EC Diffie-Hellman secret in constant time
+ *
+ *  Returns: 1: exponentiation was successful
+ *           0: scalar was invalid (zero or overflow) or hashfp returned 0
+ *  Args:    ctx:        pointer to a context object.
+ *  Out:     output:     pointer to an array to be filled by hashfp.
+ *  In:      pubkey:     pointer to a secp256k1_pubkey containing an initialized public key.
+ *           seckey:     a 32-byte scalar with which to multiply the point.
+ *           hashfp:     pointer to a hash function. If NULL,
+ *                       secp256k1_ecdh_hash_function_sha256 is used
+ *                       (in which case, 32 bytes will be written to output).
+ *           data:       arbitrary data pointer that is passed through to hashfp
+ *                       (can be NULL for secp256k1_ecdh_hash_function_sha256).
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdh(
+  const secp256k1_context *ctx,
+  unsigned char *output,
+  const secp256k1_pubkey *pubkey,
+  const unsigned char *seckey,
+  secp256k1_ecdh_hash_function hashfp,
+  void *data
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SECP256K1_ECDH_H */
diff --git a/vendor/secp256k1/include/secp256k1/secp256k1_extrakeys.h b/vendor/secp256k1/include/secp256k1/secp256k1_extrakeys.h
new file mode 100644
index 0000000..4cc6d4f
--- /dev/null
+++ b/vendor/secp256k1/include/secp256k1/secp256k1_extrakeys.h
@@ -0,0 +1,247 @@
+#ifndef SECP256K1_EXTRAKEYS_H
+#define SECP256K1_EXTRAKEYS_H
+
+#include "secp256k1.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+    /** Opaque data structure that holds a parsed and valid "x-only" public key.
+     *  An x-only pubkey encodes a point whose Y coordinate is even. It is
+     *  serialized using only its X coordinate (32 bytes). See BIP-340 for more
+     *  information about x-only pubkeys.
+     *
+     *  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, use
+     *  use secp256k1_xonly_pubkey_serialize and secp256k1_xonly_pubkey_parse. To
+     *  compare keys, use secp256k1_xonly_pubkey_cmp.
+     */
+    typedef struct {
+        unsigned char data[64];
+    } secp256k1_xonly_pubkey;
+
+    /** Opaque data structure that holds a keypair consisting of a secret and a
+     *  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 96 bytes in size, and can be safely copied/moved.
+     */
+    typedef struct {
+        unsigned char data[96];
+    } secp256k1_keypair;
+
+    /** Parse a 32-byte sequence into a xonly_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, it's set to an invalid value.
+     *  In: input32: pointer to a serialized xonly_pubkey.
+     */
+    SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_xonly_pubkey_parse(
+        const secp256k1_context* ctx,
+        secp256k1_xonly_pubkey* pubkey,
+        const unsigned char* input32
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+    /** Serialize an xonly_pubkey object into a 32-byte sequence.
+     *
+     *  Returns: 1 always.
+     *
+     *  Args:     ctx: pointer to a context object.
+     *  Out: output32: pointer to a 32-byte array to place the serialized key in.
+     *  In:    pubkey: pointer to a secp256k1_xonly_pubkey containing an initialized public key.
+     */
+    SECP256K1_API int secp256k1_xonly_pubkey_serialize(
+        const secp256k1_context* ctx,
+        unsigned char* output32,
+        const secp256k1_xonly_pubkey* pubkey
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+    /** Compare two x-only public keys using lexicographic 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 int secp256k1_xonly_pubkey_cmp(
+        const secp256k1_context* ctx,
+        const secp256k1_xonly_pubkey* pk1,
+        const secp256k1_xonly_pubkey* pk2
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+    /** Converts a secp256k1_pubkey into a secp256k1_xonly_pubkey.
+     *
+     *  Returns: 1 always.
+     *
+     *  Args:         ctx: pointer to a context object.
+     *  Out: xonly_pubkey: pointer to an x-only public key object for placing the converted public key.
+     *          pk_parity: Ignored if NULL. Otherwise, pointer to an integer that
+     *                     will be set to 1 if the point encoded by xonly_pubkey is
+     *                     the negation of the pubkey and set to 0 otherwise.
+     *  In:        pubkey: pointer to a public key that is converted.
+     */
+    SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_xonly_pubkey_from_pubkey(
+        const secp256k1_context* ctx,
+        secp256k1_xonly_pubkey* xonly_pubkey,
+        int* pk_parity,
+        const secp256k1_pubkey* pubkey
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(4);
+
+    /** Tweak an x-only public key by adding the generator multiplied with tweak32
+     *  to it.
+     *
+     *  Note that the resulting point can not in general be represented by an x-only
+     *  pubkey because it may have an odd Y coordinate. Instead, the output_pubkey
+     *  is a normal secp256k1_pubkey.
+     *
+     *  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.
+     *  Out:  output_pubkey: pointer to a public key to store the result. Will be set
+     *                       to an invalid value if this function returns 0.
+     *  In: internal_pubkey: pointer to an x-only pubkey to apply the tweak to.
+     *              tweak32: pointer to a 32-byte tweak, which must be valid
+     *                       according to secp256k1_ec_seckey_verify or 32 zero
+     *                       bytes. For uniformly random 32-byte tweaks, the chance of
+     *                       being invalid is negligible (around 1 in 2^128).
+     */
+    SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_xonly_pubkey_tweak_add(
+        const secp256k1_context* ctx,
+        secp256k1_pubkey* output_pubkey,
+        const secp256k1_xonly_pubkey* internal_pubkey,
+        const unsigned char* tweak32
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+    /** Checks that a tweaked pubkey is the result of calling
+     *  secp256k1_xonly_pubkey_tweak_add with internal_pubkey and tweak32.
+     *
+     *  The tweaked pubkey is represented by its 32-byte x-only serialization and
+     *  its pk_parity, which can both be obtained by converting the result of
+     *  tweak_add to a secp256k1_xonly_pubkey.
+     *
+     *  Note that this alone does _not_ verify that the tweaked pubkey is a
+     *  commitment. If the tweak is not chosen in a specific way, the tweaked pubkey
+     *  can easily be the result of a different internal_pubkey and tweak.
+     *
+     *  Returns: 0 if the arguments are invalid or the tweaked pubkey is not the
+     *           result of tweaking the internal_pubkey with tweak32. 1 otherwise.
+     *  Args:            ctx: pointer to a context object.
+     *  In: tweaked_pubkey32: pointer to a serialized xonly_pubkey.
+     *     tweaked_pk_parity: the parity of the tweaked pubkey (whose serialization
+     *                        is passed in as tweaked_pubkey32). This must match the
+     *                        pk_parity value that is returned when calling
+     *                        secp256k1_xonly_pubkey with the tweaked pubkey, or
+     *                        this function will fail.
+     *       internal_pubkey: pointer to an x-only public key object to apply the tweak to.
+     *               tweak32: pointer to a 32-byte tweak.
+     */
+    SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_xonly_pubkey_tweak_add_check(
+        const secp256k1_context* ctx,
+        const unsigned char* tweaked_pubkey32,
+        int tweaked_pk_parity,
+        const secp256k1_xonly_pubkey* internal_pubkey,
+        const unsigned char* tweak32
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5);
+
+    /** Compute the keypair for a secret key.
+     *
+     *  Returns: 1: secret was valid, keypair is ready to use
+     *           0: secret was invalid, try again with a different secret
+     *  Args:    ctx: pointer to a context object (not secp256k1_context_static).
+     *  Out: keypair: pointer to the created keypair.
+     *  In:   seckey: pointer to a 32-byte secret key.
+     */
+    SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_keypair_create(
+        const secp256k1_context* ctx,
+        secp256k1_keypair* keypair,
+        const unsigned char* seckey
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+    /** Get the secret key from a keypair.
+     *
+     *  Returns: 1 always.
+     *  Args:   ctx: pointer to a context object.
+     *  Out: seckey: pointer to a 32-byte buffer for the secret key.
+     *  In: keypair: pointer to a keypair.
+     */
+    SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_keypair_sec(
+        const secp256k1_context* ctx,
+        unsigned char* seckey,
+        const secp256k1_keypair* keypair
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+    /** Get the public key from a keypair.
+     *
+     *  Returns: 1 always.
+     *  Args:   ctx: pointer to a context object.
+     *  Out: pubkey: pointer to a pubkey object, set to the keypair public key.
+     *  In: keypair: pointer to a keypair.
+     */
+    SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_keypair_pub(
+        const secp256k1_context* ctx,
+        secp256k1_pubkey* pubkey,
+        const secp256k1_keypair* keypair
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+    /** Get the x-only public key from a keypair.
+     *
+     *  This is the same as calling secp256k1_keypair_pub and then
+     *  secp256k1_xonly_pubkey_from_pubkey.
+     *
+     *  Returns: 1 always.
+     *  Args:   ctx: pointer to a context object.
+     *  Out: pubkey: pointer to an xonly_pubkey object, set to the keypair
+     *               public key after converting it to an xonly_pubkey.
+     *    pk_parity: Ignored if NULL. Otherwise, pointer to an integer that will be set to the
+     *               pk_parity argument of secp256k1_xonly_pubkey_from_pubkey.
+     *  In: keypair: pointer to a keypair.
+     */
+    SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_keypair_xonly_pub(
+        const secp256k1_context* ctx,
+        secp256k1_xonly_pubkey* pubkey,
+        int* pk_parity,
+        const secp256k1_keypair* keypair
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(4);
+
+    /** Tweak a keypair by adding tweak32 to the secret key and updating the public
+     *  key accordingly.
+     *
+     *  Calling this function and then secp256k1_keypair_pub results in the same
+     *  public key as calling secp256k1_keypair_xonly_pub and then
+     *  secp256k1_xonly_pubkey_tweak_add.
+     *
+     *  Returns: 0 if the arguments are invalid or the resulting keypair would be
+     *           invalid (only when the tweak is the negation of the keypair's
+     *           secret key). 1 otherwise.
+     *
+     *  Args:       ctx: pointer to a context object.
+     *  In/Out: keypair: pointer to a keypair to apply the tweak to. Will be set to
+     *                   an invalid value if this function returns 0.
+     *  In:     tweak32: pointer to a 32-byte tweak, which must be valid according to
+     *                   secp256k1_ec_seckey_verify or 32 zero bytes. For uniformly
+     *                   random 32-byte tweaks, the chance of being invalid is
+     *                   negligible (around 1 in 2^128).
+     */
+    SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_keypair_xonly_tweak_add(
+        const secp256k1_context* ctx,
+        secp256k1_keypair* keypair,
+        const unsigned char* tweak32
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SECP256K1_EXTRAKEYS_H */
\ No newline at end of file
diff --git a/vendor/secp256k1/include/secp256k1/secp256k1_schnorrsig.h b/vendor/secp256k1/include/secp256k1/secp256k1_schnorrsig.h
new file mode 100644
index 0000000..5c338f4
--- /dev/null
+++ b/vendor/secp256k1/include/secp256k1/secp256k1_schnorrsig.h
@@ -0,0 +1,190 @@
+#ifndef SECP256K1_SCHNORRSIG_H
+#define SECP256K1_SCHNORRSIG_H
+
+#include "secp256k1.h"
+#include "secp256k1_extrakeys.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+    /** This module implements a variant of Schnorr signatures compliant with
+     *  Bitcoin Improvement Proposal 340 "Schnorr Signatures for secp256k1"
+     *  (https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki).
+     */
+
+     /** A pointer to a function to deterministically generate a nonce.
+      *
+      *  Same as secp256k1_nonce function with the exception of accepting an
+      *  additional pubkey argument and not requiring an attempt argument. The pubkey
+      *  argument can protect signature schemes with key-prefixed challenge hash
+      *  inputs against reusing the nonce when signing with the wrong precomputed
+      *  pubkey.
+      *
+      *  Returns: 1 if a nonce was successfully generated. 0 will cause signing to
+      *           return an error.
+      *  Out:  nonce32: pointer to a 32-byte array to be filled by the function
+      *  In:       msg: the message being verified. Is NULL if and only if msglen
+      *                 is 0.
+      *         msglen: the length of the message
+      *          key32: pointer to a 32-byte secret key (will not be NULL)
+      *     xonly_pk32: the 32-byte serialized xonly pubkey corresponding to key32
+      *                 (will not be NULL)
+      *           algo: pointer to an array describing the signature
+      *                 algorithm (will not be NULL)
+      *        algolen: the length of the algo array
+      *           data: arbitrary data pointer that is passed through
+      *
+      *  Except for test cases, this function should compute some cryptographic hash of
+      *  the message, the key, the pubkey, the algorithm description, and data.
+      */
+    typedef int (*secp256k1_nonce_function_hardened)(
+        unsigned char* nonce32,
+        const unsigned char* msg,
+        size_t msglen,
+        const unsigned char* key32,
+        const unsigned char* xonly_pk32,
+        const unsigned char* algo,
+        size_t algolen,
+        void* data
+        );
+
+    /** An implementation of the nonce generation function as defined in Bitcoin
+     *  Improvement Proposal 340 "Schnorr Signatures for secp256k1"
+     *  (https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki).
+     *
+     *  If a data pointer is passed, it is assumed to be a pointer to 32 bytes of
+     *  auxiliary random data as defined in BIP-340. If the data pointer is NULL,
+     *  the nonce derivation procedure follows BIP-340 by setting the auxiliary
+     *  random data to zero. The algo argument must be non-NULL, otherwise the
+     *  function will fail and return 0. The hash will be tagged with algo.
+     *  Therefore, to create BIP-340 compliant signatures, algo must be set to
+     *  "BIP0340/nonce" and algolen to 13.
+     */
+    SECP256K1_API const secp256k1_nonce_function_hardened secp256k1_nonce_function_bip340;
+
+    /** Data structure that contains additional arguments for schnorrsig_sign_custom.
+     *
+     *  A schnorrsig_extraparams structure object can be initialized correctly by
+     *  setting it to SECP256K1_SCHNORRSIG_EXTRAPARAMS_INIT.
+     *
+     *  Members:
+     *      magic: set to SECP256K1_SCHNORRSIG_EXTRAPARAMS_MAGIC at initialization
+     *             and has no other function than making sure the object is
+     *             initialized.
+     *    noncefp: pointer to a nonce generation function. If NULL,
+     *             secp256k1_nonce_function_bip340 is used
+     *      ndata: pointer to arbitrary data used by the nonce generation function
+     *             (can be NULL). If it is non-NULL and
+     *             secp256k1_nonce_function_bip340 is used, then ndata must be a
+     *             pointer to 32-byte auxiliary randomness as per BIP-340.
+     */
+    typedef struct {
+        unsigned char magic[4];
+        secp256k1_nonce_function_hardened noncefp;
+        void* ndata;
+    } secp256k1_schnorrsig_extraparams;
+
+#define SECP256K1_SCHNORRSIG_EXTRAPARAMS_MAGIC { 0xda, 0x6f, 0xb3, 0x8c }
+#define SECP256K1_SCHNORRSIG_EXTRAPARAMS_INIT {\
+    SECP256K1_SCHNORRSIG_EXTRAPARAMS_MAGIC,\
+    NULL,\
+    NULL\
+}
+
+    /** Create a Schnorr signature.
+     *
+     *  Does _not_ strictly follow BIP-340 because it does not verify the resulting
+     *  signature. Instead, you can manually use secp256k1_schnorrsig_verify and
+     *  abort if it fails.
+     *
+     *  This function only signs 32-byte messages. If you have messages of a
+     *  different size (or the same size but without a context-specific tag
+     *  prefix), it is recommended to create a 32-byte message hash with
+     *  secp256k1_tagged_sha256 and then sign the hash. Tagged hashing allows
+     *  providing an context-specific tag for domain separation. This prevents
+     *  signatures from being valid in multiple contexts by accident.
+     *
+     *  Returns 1 on success, 0 on failure.
+     *  Args:    ctx: pointer to a context object (not secp256k1_context_static).
+     *  Out:   sig64: pointer to a 64-byte array to store the serialized signature.
+     *  In:    msg32: the 32-byte message being signed.
+     *       keypair: pointer to an initialized keypair.
+     *    aux_rand32: 32 bytes of fresh randomness. While recommended to provide
+     *                this, it is only supplemental to security and can be NULL. A
+     *                NULL argument is treated the same as an all-zero one. See
+     *                BIP-340 "Default Signing" for a full explanation of this
+     *                argument and for guidance if randomness is expensive.
+     */
+    SECP256K1_API int secp256k1_schnorrsig_sign32(
+        const secp256k1_context* ctx,
+        unsigned char* sig64,
+        const unsigned char* msg32,
+        const secp256k1_keypair* keypair,
+        const unsigned char* aux_rand32
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+    /** Same as secp256k1_schnorrsig_sign32, but DEPRECATED. Will be removed in
+     *  future versions. */
+    SECP256K1_API int secp256k1_schnorrsig_sign(
+        const secp256k1_context* ctx,
+        unsigned char* sig64,
+        const unsigned char* msg32,
+        const secp256k1_keypair* keypair,
+        const unsigned char* aux_rand32
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4)
+        SECP256K1_DEPRECATED("Use secp256k1_schnorrsig_sign32 instead");
+
+    /** Create a Schnorr signature with a more flexible API.
+     *
+     *  Same arguments as secp256k1_schnorrsig_sign except that it allows signing
+     *  variable length messages and accepts a pointer to an extraparams object that
+     *  allows customizing signing by passing additional arguments.
+     *
+     *  Equivalent to secp256k1_schnorrsig_sign32(..., aux_rand32) if msglen is 32
+     *  and extraparams is initialized as follows:
+     *  ```
+     *  secp256k1_schnorrsig_extraparams extraparams = SECP256K1_SCHNORRSIG_EXTRAPARAMS_INIT;
+     *  extraparams.ndata = (unsigned char*)aux_rand32;
+     *  ```
+     *
+     *  Returns 1 on success, 0 on failure.
+     *  Args:   ctx: pointer to a context object (not secp256k1_context_static).
+     *  Out:  sig64: pointer to a 64-byte array to store the serialized signature.
+     *  In:     msg: the message being signed. Can only be NULL if msglen is 0.
+     *       msglen: length of the message.
+     *      keypair: pointer to an initialized keypair.
+     *  extraparams: pointer to an extraparams object (can be NULL).
+     */
+    SECP256K1_API int secp256k1_schnorrsig_sign_custom(
+        const secp256k1_context* ctx,
+        unsigned char* sig64,
+        const unsigned char* msg,
+        size_t msglen,
+        const secp256k1_keypair* keypair,
+        secp256k1_schnorrsig_extraparams* extraparams
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(5);
+
+    /** Verify a Schnorr signature.
+     *
+     *  Returns: 1: correct signature
+     *           0: incorrect signature
+     *  Args:    ctx: pointer to a context object.
+     *  In:    sig64: pointer to the 64-byte signature to verify.
+     *           msg: the message being verified. Can only be NULL if msglen is 0.
+     *        msglen: length of the message
+     *        pubkey: pointer to an x-only public key to verify with
+     */
+    SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_schnorrsig_verify(
+        const secp256k1_context* ctx,
+        const unsigned char* sig64,
+        const unsigned char* msg,
+        size_t msglen,
+        const secp256k1_xonly_pubkey* pubkey
+    ) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(5);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SECP256K1_SCHNORRSIG_H */