Squashed commit of the following:

commit 942aed8a4e7c173a2c9423829c2b38087cbd49e4
Author: vnugent <public@vaughnnugent.com>
Date:   Tue Aug 6 20:54:03 2024 -0400

    chore: update changelog and mbedtls headers

commit 3b97f84fd0477eafcd6567eb8597b213e4136664
Author: vnugent <public@vaughnnugent.com>
Date:   Tue Aug 6 19:57:10 2024 -0400

    update libsecp256k1 to v0.5.1

commit 7989a2660997b909e0b99fc1dfb3bcfbb0528df3
Author: vnugent <public@vaughnnugent.com>
Date:   Tue Aug 6 19:42:25 2024 -0400

    update openssl to 3.3.1

commit e949ae5aa1fd25d4d11fe31e30b7d82ae7778dc2
Author: vnugent <public@vaughnnugent.com>
Date:   Mon Aug 5 18:01:03 2024 -0400

    fix: Find and fix openssl encryption bug

commit a60a3e1ca1d99d655c0cfc96e3952c371e8a8677
Author: vnugent <public@vaughnnugent.com>
Date:   Sun Aug 4 15:27:06 2024 -0400

    cleanup comments + return codes

commit 2aa7f4b6cdb2e0e8990e7177476f4104fd2e2b17
Author: vnugent <public@vaughnnugent.com>
Date:   Sat Jul 27 22:20:53 2024 -0400

    fix codeberg url

commit 1640f79776c6b291b49a39a6128c05888fc4153e
Author: vnugent <public@vaughnnugent.com>
Date:   Sat Jul 27 00:05:07 2024 -0400

    fix: Potential overflow in nip44 padding calculation

commit 07de078a3b5b7b0043d9f81bb5a9e750a3a0c7c1
Author: vnugent <public@vaughnnugent.com>
Date:   Fri Jul 26 23:37:15 2024 -0400

    refactor: Span invasion, checks and fix some evp api

commit 54f520e4bfc0fe23e2719d44b09739aa8709451c
Author: vnugent <public@vaughnnugent.com>
Date:   Tue Jul 23 19:55:13 2024 -0400

    latest changes

commit 12feb33dba2061415d6f39fa59dec16fafcda2a0
Author: vnugent <public@vaughnnugent.com>
Date:   Sun Jul 21 17:51:04 2024 -0400

    Push latest changes, patches, and internal upgrades

commit ffe42b6858f112a00405be4f0605ab1163063749
Author: vnugent <public@vaughnnugent.com>
Date:   Sat Jul 13 22:13:13 2024 -0400

    test: Add decryption test cases and fixes

commit 5dfafbc5a9214587533ec8b1dae2a962118d3650
Author: vnugent <public@vaughnnugent.com>
Date:   Fri Jul 12 22:14:00 2024 -0400

    feat: add decryption functionality to public api

commit 8df8c5aed4ac626171b451b5422c3b207e88000b
Author: vnugent <public@vaughnnugent.com>
Date:   Thu Jul 11 21:39:39 2024 -0400

    feat: Update sidecar utils library

commit 23fe6e8c8596333c2183f0f4389817087442c551
Author: vnugent <public@vaughnnugent.com>
Date:   Fri Jul 5 00:03:48 2024 -0400

    push latest utils and changes

commit dc71f861df8929deee300368b88ef47d45560695
Author: vnugent <public@vaughnnugent.com>
Date:   Mon Jul 1 15:05:34 2024 -0400

    fix: #7 fix confusing inline functions

commit 90166048046d2511f0bb74f8880180e82466d4c0
Author: vnugent <public@vaughnnugent.com>
Date:   Tue Jun 18 21:22:37 2024 -0400

    push pending changes

commit 461dd71069d0c0250752ac1256160605c33a6243
Author: vnugent <public@vaughnnugent.com>
Date:   Tue Jun 11 15:44:28 2024 -0400

    feat!: #4 Close #4. Add public nip04 support to api

commit a74f96251bcc81fb2c94fe75dd6f8043fd35fe0b
Merge: 1c26ef8 51d0aff
Author: vnugent <public@vaughnnugent.com>
Date:   Wed May 29 13:37:00 2024 -0400

    Merge branch 'master' into develop

commit 1c26ef86a04690120f4f752c7c5018a570ec5880
Author: vnugent <public@vaughnnugent.com>
Date:   Wed May 29 13:34:20 2024 -0400

    missed extra argument

commit 88c9095743a12cf8fc1793c607ba3a1e4fa86483
Author: vnugent <public@vaughnnugent.com>
Date:   Wed May 29 13:25:51 2024 -0400

    refactor!: return NC_SUCCESS when validating secret key

commit 718be80a4810b9352de7eb0707da54020aa6b649
Author: vnugent <public@vaughnnugent.com>
Date:   Mon May 27 14:52:41 2024 -0400

    fix: Properly build mbedtls & cmake fixes

commit a8a6efb2319f739e5faae550561dc27d9dd1e88d
Author: vnugent <public@vaughnnugent.com>
Date:   Sun May 26 17:39:40 2024 -0400

    chore: Update libs, reorder files, internalize private headers

commit 72e1b7be4031e2fd4d258fcf434ad049c0029201
Author: vnugent <public@vaughnnugent.com>
Date:   Sun May 26 13:39:08 2024 -0400

    fix: Add c++ extern prototypes in noscrypt.h

commit aeaac8d328b75911541be64d6f09d58fca294a08
Author: vnugent <public@vaughnnugent.com>
Date:   Sun May 26 11:47:17 2024 -0400

    refactor: Dep update, openssl chacha20 added

commit 86b02540cce6015cfe4a2a56499a9a2f45d4e368
Author: vnugent <public@vaughnnugent.com>
Date:   Sat May 18 12:24:17 2024 -0400

    refactor: Remove NCContext structure definition

commit d09d9330415d463ca19be9394b02ce11b3366f7e
Author: vnugent <public@vaughnnugent.com>
Date:   Mon May 13 22:33:50 2024 -0400

    fix: update mbedtls inline issue includes

commit 7838cb4bb15d4f453f92f56ece75e2b03986fe42
Author: vnugent <public@vaughnnugent.com>
Date:   Mon May 13 22:29:16 2024 -0400

    fix: force fPIC for secp256k1 targets

commit d76f7708bc6ae81a638ca708230ac9153ac754e2
Merge: aa8033d a526139
Author: vnugent <public@vaughnnugent.com>
Date:   Sun May 12 00:37:01 2024 -0400

    Merge branch 'master' into develop

commit aa8033d4dbfebeb72b6fd7a0cd218ebde0eb54dd
Author: vnugent <public@vaughnnugent.com>
Date:   Sun May 12 00:34:20 2024 -0400

    Final overview and test before tag

commit 4e3ead2cf1d3068e77f0959dfdc17e20e9102a0f
Merge: 2cee801 872c49d
Author: vnugent <public@vaughnnugent.com>
Date:   Mon May 6 22:08:09 2024 -0400

    Merge branch 'master' into develop

commit 2cee801979bfbcb3b0e53f592ce8c779b57cb679
Author: vnugent <public@vaughnnugent.com>
Date:   Mon May 6 22:02:39 2024 -0400

    Ensure static and dynamic libs get same args

commit f533694023133552d0d42933d779c95a5854343f
Author: vnugent <public@vaughnnugent.com>
Date:   Mon May 6 21:50:29 2024 -0400

    feat: CMake install & fetch-content test & updates

commit 940ff20348b13d0bc30d9e9f4289dd6de20b16ba
Author: vnugent <public@vaughnnugent.com>
Date:   Sun May 5 14:07:28 2024 -0400

    codeberg readonly push

commit b34ed055c0b7d143561ce8798e0a95313b9224bd
Merge: 0a40e20 e737556
Author: vnugent <public@vaughnnugent.com>
Date:   Sat May 4 14:06:45 2024 -0400

    Merge branch 'master' into develop

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

2 files changed, 313 insertions, 0 deletions

diff --git a/vendor/secp256k1/include/secp256k1/secp256k1_ellswift.h b/vendor/secp256k1/include/secp256k1/secp256k1_ellswift.h
new file mode 100644
index 0000000..ae37287
--- /dev/null
+++ b/vendor/secp256k1/include/secp256k1/secp256k1_ellswift.h
@@ -0,0 +1,200 @@
+#ifndef SECP256K1_ELLSWIFT_H
+#define SECP256K1_ELLSWIFT_H
+
+#include "secp256k1.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* This module provides an implementation of ElligatorSwift as well as a
+ * version of x-only ECDH using it (including compatibility with BIP324).
+ *
+ * ElligatorSwift is described in https://eprint.iacr.org/2022/759 by
+ * Chavez-Saab, Rodriguez-Henriquez, and Tibouchi. It permits encoding
+ * uniformly chosen public keys as 64-byte arrays which are indistinguishable
+ * from uniformly random arrays.
+ *
+ * Let f be the function from pairs of field elements to point X coordinates,
+ * defined as follows (all operations modulo p = 2^256 - 2^32 - 977)
+ * f(u,t):
+ * - Let C = 0xa2d2ba93507f1df233770c2a797962cc61f6d15da14ecd47d8d27ae1cd5f852,
+ *   a square root of -3.
+ * - If u=0, set u=1 instead.
+ * - If t=0, set t=1 instead.
+ * - If u^3 + t^2 + 7 = 0, multiply t by 2.
+ * - Let X = (u^3 + 7 - t^2) / (2 * t)
+ * - Let Y = (X + t) / (C * u)
+ * - Return the first in [u + 4 * Y^2, (-X/Y - u) / 2, (X/Y - u) / 2] that is an
+ *   X coordinate on the curve (at least one of them is, for any u and t).
+ *
+ * Then an ElligatorSwift encoding of x consists of the 32-byte big-endian
+ * encodings of field elements u and t concatenated, where f(u,t) = x.
+ * The encoding algorithm is described in the paper, and effectively picks a
+ * uniformly random pair (u,t) among those which encode x.
+ *
+ * If the Y coordinate is relevant, it is given the same parity as t.
+ *
+ * Changes w.r.t. the the paper:
+ * - The u=0, t=0, and u^3+t^2+7=0 conditions result in decoding to the point
+ *   at infinity in the paper. Here they are remapped to finite points.
+ * - The paper uses an additional encoding bit for the parity of y. Here the
+ *   parity of t is used (negating t does not affect the decoded x coordinate,
+ *   so this is possible).
+ *
+ * For mathematical background about the scheme, see the doc/ellswift.md file.
+ */
+
+/** A pointer to a function used by secp256k1_ellswift_xdh to hash the shared X
+ *  coordinate along with the encoded public keys to a uniform shared secret.
+ *
+ *  Returns: 1 if a shared secret was successfully computed.
+ *           0 will cause secp256k1_ellswift_xdh to fail and return 0.
+ *           Other return values are not allowed, and the behaviour of
+ *           secp256k1_ellswift_xdh is undefined for other return values.
+ *  Out:     output:     pointer to an array to be filled by the function
+ *  In:      x32:        pointer to the 32-byte serialized X coordinate
+ *                       of the resulting shared point (will not be NULL)
+ *           ell_a64:    pointer to the 64-byte encoded public key of party A
+ *                       (will not be NULL)
+ *           ell_b64:    pointer to the 64-byte encoded public key of party B
+ *                       (will not be NULL)
+ *           data:       arbitrary data pointer that is passed through
+ */
+typedef int (*secp256k1_ellswift_xdh_hash_function)(
+    unsigned char *output,
+    const unsigned char *x32,
+    const unsigned char *ell_a64,
+    const unsigned char *ell_b64,
+    void *data
+);
+
+/** An implementation of an secp256k1_ellswift_xdh_hash_function which uses
+ *  SHA256(prefix64 || ell_a64 || ell_b64 || x32), where prefix64 is the 64-byte
+ *  array pointed to by data. */
+SECP256K1_API const secp256k1_ellswift_xdh_hash_function secp256k1_ellswift_xdh_hash_function_prefix;
+
+/** An implementation of an secp256k1_ellswift_xdh_hash_function compatible with
+ *  BIP324. It returns H_tag(ell_a64 || ell_b64 || x32), where H_tag is the
+ *  BIP340 tagged hash function with tag "bip324_ellswift_xonly_ecdh". Equivalent
+ *  to secp256k1_ellswift_xdh_hash_function_prefix with prefix64 set to
+ *  SHA256("bip324_ellswift_xonly_ecdh")||SHA256("bip324_ellswift_xonly_ecdh").
+ *  The data argument is ignored. */
+SECP256K1_API const secp256k1_ellswift_xdh_hash_function secp256k1_ellswift_xdh_hash_function_bip324;
+
+/** Construct a 64-byte ElligatorSwift encoding of a given pubkey.
+ *
+ *  Returns: 1 always.
+ *  Args:    ctx:        pointer to a context object
+ *  Out:     ell64:      pointer to a 64-byte array to be filled
+ *  In:      pubkey:     pointer to a secp256k1_pubkey containing an
+ *                       initialized public key
+ *           rnd32:      pointer to 32 bytes of randomness
+ *
+ * It is recommended that rnd32 consists of 32 uniformly random bytes, not
+ * known to any adversary trying to detect whether public keys are being
+ * encoded, though 16 bytes of randomness (padded to an array of 32 bytes,
+ * e.g., with zeros) suffice to make the result indistinguishable from
+ * uniform. The randomness in rnd32 must not be a deterministic function of
+ * the pubkey (it can be derived from the private key, though).
+ *
+ * It is not guaranteed that the computed encoding is stable across versions
+ * of the library, even if all arguments to this function (including rnd32)
+ * are the same.
+ *
+ * This function runs in variable time.
+ */
+SECP256K1_API int secp256k1_ellswift_encode(
+    const secp256k1_context *ctx,
+    unsigned char *ell64,
+    const secp256k1_pubkey *pubkey,
+    const unsigned char *rnd32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+/** Decode a 64-bytes ElligatorSwift encoded public key.
+ *
+ *  Returns: always 1
+ *  Args:    ctx:        pointer to a context object
+ *  Out:     pubkey:     pointer to a secp256k1_pubkey that will be filled
+ *  In:      ell64:      pointer to a 64-byte array to decode
+ *
+ * This function runs in variable time.
+ */
+SECP256K1_API int secp256k1_ellswift_decode(
+    const secp256k1_context *ctx,
+    secp256k1_pubkey *pubkey,
+    const unsigned char *ell64
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Compute an ElligatorSwift public key for a secret key.
+ *
+ *  Returns: 1: secret was valid, public key was stored.
+ *           0: secret was invalid, try again.
+ *  Args:    ctx:        pointer to a context object
+ *  Out:     ell64:      pointer to a 64-byte array to receive the ElligatorSwift
+ *                       public key
+ *  In:      seckey32:   pointer to a 32-byte secret key
+ *           auxrnd32:   (optional) pointer to 32 bytes of randomness
+ *
+ * Constant time in seckey and auxrnd32, but not in the resulting public key.
+ *
+ * It is recommended that auxrnd32 contains 32 uniformly random bytes, though
+ * it is optional (and does result in encodings that are indistinguishable from
+ * uniform even without any auxrnd32). It differs from the (mandatory) rnd32
+ * argument to secp256k1_ellswift_encode in this regard.
+ *
+ * This function can be used instead of calling secp256k1_ec_pubkey_create
+ * followed by secp256k1_ellswift_encode. It is safer, as it uses the secret
+ * key as entropy for the encoding (supplemented with auxrnd32, if provided).
+ *
+ * Like secp256k1_ellswift_encode, this function does not guarantee that the
+ * computed encoding is stable across versions of the library, even if all
+ * arguments (including auxrnd32) are the same.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ellswift_create(
+    const secp256k1_context *ctx,
+    unsigned char *ell64,
+    const unsigned char *seckey32,
+    const unsigned char *auxrnd32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Given a private key, and ElligatorSwift public keys sent in both directions,
+ *  compute a shared secret using x-only Elliptic Curve Diffie-Hellman (ECDH).
+ *
+ *  Returns: 1: shared secret was successfully computed
+ *           0: secret was invalid or hashfp returned 0
+ *  Args:    ctx:       pointer to a context object.
+ *  Out:     output:    pointer to an array to be filled by hashfp.
+ *  In:      ell_a64:   pointer to the 64-byte encoded public key of party A
+ *                      (will not be NULL)
+ *           ell_b64:   pointer to the 64-byte encoded public key of party B
+ *                      (will not be NULL)
+ *           seckey32:  pointer to our 32-byte secret key
+ *           party:     boolean indicating which party we are: zero if we are
+ *                      party A, non-zero if we are party B. seckey32 must be
+ *                      the private key corresponding to that party's ell_?64.
+ *                      This correspondence is not checked.
+ *           hashfp:    pointer to a hash function.
+ *           data:      arbitrary data pointer passed through to hashfp.
+ *
+ * Constant time in seckey32.
+ *
+ * This function is more efficient than decoding the public keys, and performing
+ * ECDH on them.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ellswift_xdh(
+  const secp256k1_context *ctx,
+  unsigned char *output,
+  const unsigned char *ell_a64,
+  const unsigned char *ell_b64,
+  const unsigned char *seckey32,
+  int party,
+  secp256k1_ellswift_xdh_hash_function hashfp,
+  void *data
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4) SECP256K1_ARG_NONNULL(5) SECP256K1_ARG_NONNULL(7);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SECP256K1_ELLSWIFT_H */
diff --git a/vendor/secp256k1/include/secp256k1/secp256k1_recovery.h b/vendor/secp256k1/include/secp256k1/secp256k1_recovery.h
new file mode 100644
index 0000000..341b8ba
--- /dev/null
+++ b/vendor/secp256k1/include/secp256k1/secp256k1_recovery.h
@@ -0,0 +1,113 @@
+#ifndef SECP256K1_RECOVERY_H
+#define SECP256K1_RECOVERY_H
+
+#include "secp256k1.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** Opaque data structured that holds a parsed ECDSA signature,
+ *  supporting pubkey recovery.
+ *
+ *  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 65 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_parse_* functions.
+ *
+ *  Furthermore, it is guaranteed that identical signatures (including their
+ *  recoverability) will have identical representation, so they can be
+ *  memcmp'ed.
+ */
+typedef struct {
+    unsigned char data[65];
+} secp256k1_ecdsa_recoverable_signature;
+
+/** Parse a compact ECDSA signature (64 bytes + recovery id).
+ *
+ *  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 a 64-byte compact signature
+ *        recid:   the recovery id (0, 1, 2 or 3)
+ */
+SECP256K1_API int secp256k1_ecdsa_recoverable_signature_parse_compact(
+    const secp256k1_context *ctx,
+    secp256k1_ecdsa_recoverable_signature *sig,
+    const unsigned char *input64,
+    int recid
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Convert a recoverable signature into a normal signature.
+ *
+ *  Returns: 1
+ *  Args: ctx:    pointer to a context object.
+ *  Out:  sig:    pointer to a normal signature.
+ *  In:   sigin:  pointer to a recoverable signature.
+ */
+SECP256K1_API int secp256k1_ecdsa_recoverable_signature_convert(
+    const secp256k1_context *ctx,
+    secp256k1_ecdsa_signature *sig,
+    const secp256k1_ecdsa_recoverable_signature *sigin
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3);
+
+/** Serialize an ECDSA signature in compact format (64 bytes + recovery id).
+ *
+ *  Returns: 1
+ *  Args: ctx:      pointer to a context object.
+ *  Out:  output64: pointer to a 64-byte array of the compact signature.
+ *        recid:    pointer to an integer to hold the recovery id.
+ *  In:   sig:      pointer to an initialized signature object.
+ */
+SECP256K1_API int secp256k1_ecdsa_recoverable_signature_serialize_compact(
+    const secp256k1_context *ctx,
+    unsigned char *output64,
+    int *recid,
+    const secp256k1_ecdsa_recoverable_signature *sig
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+/** Create a recoverable 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 for secp256k1_nonce_function_default).
+ */
+SECP256K1_API int secp256k1_ecdsa_sign_recoverable(
+    const secp256k1_context *ctx,
+    secp256k1_ecdsa_recoverable_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);
+
+/** Recover an ECDSA public key from a signature.
+ *
+ *  Returns: 1: public key successfully recovered (which guarantees a correct signature).
+ *           0: otherwise.
+ *  Args:    ctx:       pointer to a context object.
+ *  Out:     pubkey:    pointer to the recovered public key.
+ *  In:      sig:       pointer to initialized signature that supports pubkey recovery.
+ *           msghash32: the 32-byte message hash assumed to be signed.
+ */
+SECP256K1_API SECP256K1_WARN_UNUSED_RESULT int secp256k1_ecdsa_recover(
+    const secp256k1_context *ctx,
+    secp256k1_pubkey *pubkey,
+    const secp256k1_ecdsa_recoverable_signature *sig,
+    const unsigned char *msghash32
+) SECP256K1_ARG_NONNULL(1) SECP256K1_ARG_NONNULL(2) SECP256K1_ARG_NONNULL(3) SECP256K1_ARG_NONNULL(4);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SECP256K1_RECOVERY_H */