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

6 files changed, 1109 insertions, 0 deletions

diff --git a/src/crypto/hkdf.c b/src/crypto/hkdf.c
new file mode 100644
index 0000000..0d91d14
--- /dev/null
+++ b/src/crypto/hkdf.c
@@ -0,0 +1,131 @@
+/*
+* Copyright (c) 2024 Vaughn Nugent
+*
+* Package: noscrypt
+* File: hkdf.c
+*
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public License
+* as published by the Free Software Foundation; either version 2.1
+* of the License, or  (at your option) any later version.
+*
+* This library is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+* Lesser General Public License for more details.
+*
+* You should have received a copy of the GNU Lesser General Public License
+* along with noscrypt. If not, see http://www.gnu.org/licenses/.
+*/
+
+
+#include "hkdf.h"
+
+/* Include string for memmove */
+#include <string.h>
+
+#define HKDF_MIN(a, b) (a < b ? a : b)
+
+STATIC_ASSERT(HKDF_IN_BUF_SIZE > SHA256_DIGEST_SIZE, "HDK Buffer must be at least the size of the underlying hashing alg output")
+
+static _nc_fn_inline void ncWriteSpanS(span_t* span, uint32_t offset, const uint8_t* data, uint32_t size)
+{
+	DEBUG_ASSERT2(span != NULL, "Expected span to be non-null")
+	DEBUG_ASSERT2(data != NULL, "Expected data to be non-null")
+	DEBUG_ASSERT2(offset + size <= span->size, "Expected offset + size to be less than span size")
+
+	/* Copy data to span */
+	memmove(span->data + offset, data, size);
+}
+
+static _nc_fn_inline void debugValidateHandler(const struct nc_hkdf_fn_cb_struct* handler)
+{
+	DEBUG_ASSERT(handler != NULL)
+	DEBUG_ASSERT(handler->update != NULL)
+	DEBUG_ASSERT(handler->finish != NULL)
+}
+
+/*
+* The following functions implements the HKDF expand function using an existing
+* HMAC function.
+*
+* This follows the guidence from RFC 5869: https://tools.ietf.org/html/rfc5869
+*/
+
+cstatus_t hkdfExpandProcess(
+	const struct nc_hkdf_fn_cb_struct* handler,
+	void* ctx,
+	const cspan_t* info,
+	span_t* okm
+)
+{
+	cstatus_t result;
+
+	uint8_t counter;
+	uint32_t tLen, okmOffset;
+	uint8_t t[HKDF_IN_BUF_SIZE];
+	cspan_t tSpan, counterSpan;
+
+	debugValidateHandler(handler);
+
+	ncCryptoSecureZero(t, sizeof(t));
+
+	tLen = 0;				/* T(0) is an empty string(zero length) */
+	okmOffset = 0;
+	counter = 1;			/* counter is offset by 1 for init */
+	result = CSTATUS_FAIL;	/* Start in fail state */
+
+	/* counter as a span */
+	ncSpanInitC(&counterSpan, &counter, sizeof(counter));
+
+	/* Compute T(N) = HMAC(prk, T(n-1) | info | n) */
+	while (okmOffset < okm->size)
+	{
+		ncSpanInitC(&tSpan, t, tLen);
+
+		if (handler->update(ctx, &tSpan) != CSTATUS_OK)
+		{
+			goto Exit;
+		}
+
+		if (handler->update(ctx, info) != CSTATUS_OK)
+		{
+			goto Exit;
+		}
+
+		if (handler->update(ctx, &counterSpan) != CSTATUS_OK)
+		{
+			goto Exit;
+		}
+
+		/* 
+		* Write current hash state to t buffer. It is known
+		* that the t buffer must be at least the size of the
+		* underlying hash function output.
+		*/
+		if (handler->finish(ctx, t) != CSTATUS_OK)
+		{
+			goto Exit;
+		}
+
+		/* tlen becomes the hash size or remaining okm size */
+		tLen = HKDF_MIN(okm->size - okmOffset, SHA256_DIGEST_SIZE);
+
+		DEBUG_ASSERT(tLen <= sizeof(t));
+
+		/* write the T buffer back to okm */
+		ncWriteSpanS(okm, okmOffset, t, tLen);
+
+		/* shift base okm pointer by T */
+		okmOffset += tLen;
+
+		/* increment counter */
+		counter++;
+	}
+
+	result = CSTATUS_OK;	/* HMAC operation completed, so set success */
+
+Exit:
+
+	return result;
+}
diff --git a/src/crypto/impl/bcrypt.c b/src/crypto/impl/bcrypt.c
new file mode 100644
index 0000000..9b01cac
--- /dev/null
+++ b/src/crypto/impl/bcrypt.c
@@ -0,0 +1,263 @@
+/*
+* Copyright (c) 2024 Vaughn Nugent
+*
+* Package: noscrypt
+* File: impl/bcrypt.c
+*
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public License
+* as published by the Free Software Foundation; either version 2.1
+* of the License, or  (at your option) any later version.
+*
+* This library is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+* Lesser General Public License for more details.
+*
+* You should have received a copy of the GNU Lesser General Public License
+* along with noscrypt. If not, see http://www.gnu.org/licenses/.
+*/
+
+
+/*
+*	This file provides as many fallback implementations on Windows plaforms
+*	as possible using the bcrypt library. This file should be included behind
+*	other libarry implementations, as it is a fallback.
+*/
+
+#ifdef _NC_IS_WINDOWS
+
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#include <bcrypt.h>
+
+#include "nc-util.h"
+#include "hkdf.h"
+
+#define IF_BC_FAIL(x) if(!BCRYPT_SUCCESS(x)) 
+#define BC_FAIL(x) if(!BCRYPT_SUCCESS(x)) return CSTATUS_FAIL;
+
+struct _bcrypt_ctx
+{
+	BCRYPT_ALG_HANDLE hAlg;
+	BCRYPT_HASH_HANDLE hHash;
+};
+
+_IMPLSTB NTSTATUS _bcInitSha256(struct _bcrypt_ctx* ctx, DWORD flags)
+{
+	NTSTATUS result;
+
+	result = BCryptOpenAlgorithmProvider(
+		&ctx->hAlg, 
+		BCRYPT_SHA256_ALGORITHM, 
+		NULL, 
+		flags
+	);
+
+	/*
+	*  If operation failed, ensure the algorithm handle is null
+	* to make free code easier to cleanup
+	*/
+	if (!BCRYPT_SUCCESS(result))
+	{
+		ctx->hAlg = NULL;
+	}
+
+	return result;
+}
+
+_IMPLSTB NTSTATUS _bcCreateHmac(struct _bcrypt_ctx* ctx, const cspan_t* key)
+{
+	/*
+	 * NOTE: 
+	 * I am not explicitly managing the update object buffer. By setting 
+	 * the update object to NULL, and length to 0, the buffer will be
+	 * managed by the bcrypt library.
+	 * 
+	 * See: https://learn.microsoft.com/en-us/windows/win32/api/bcrypt/nf-bcrypt-bcryptcreatehash
+	 */
+
+	return BCryptCreateHash(
+		ctx->hAlg, 
+		&ctx->hHash, 
+		NULL, 
+		0, 
+		(uint8_t*)key->data, 
+		key->size, 
+		BCRYPT_HASH_REUSABLE_FLAG	/* Enable reusable for expand function */
+	);
+}
+
+_IMPLSTB NTSTATUS _bcCreate(struct _bcrypt_ctx* ctx)
+{
+	cspan_t key;
+	
+	/* Zero out key span for 0 size and NULL data ptr */
+	SecureZeroMemory(&key, sizeof(cspan_t));
+
+	return _bcCreateHmac(ctx, &key);
+}
+
+_IMPLSTB NTSTATUS _bcHashDataRaw(const struct _bcrypt_ctx* ctx, const uint8_t* data, uint32_t len)
+{
+	return BCryptHashData(ctx->hHash, (uint8_t*)data, len, 0);
+}
+
+_IMPLSTB NTSTATUS _bcHashData(const struct _bcrypt_ctx* ctx, const cspan_t* data)
+{
+	return _bcHashDataRaw(ctx, data->data, data->size);
+}
+
+_IMPLSTB NTSTATUS _bcFinishHash(const struct _bcrypt_ctx* ctx, sha256_t digestOut32)
+{
+	return BCryptFinishHash(ctx->hHash, digestOut32, sizeof(sha256_t), 0);
+}
+
+_IMPLSTB void _bcDestroyCtx(struct _bcrypt_ctx* ctx)
+{
+	/* Free the update memory if it was allocated */
+	if(ctx->hHash) BCryptDestroyHash(ctx->hHash);
+	
+	/* Close the algorithm provider */
+	if (ctx->hAlg) BCryptCloseAlgorithmProvider(ctx->hAlg, 0);
+
+	ctx->hAlg = NULL;
+	ctx->hHash = NULL;
+}
+
+#ifndef _IMPL_SECURE_ZERO_MEMSET
+	/*
+	* On Windows, we can use SecureZeroMemory
+	* as platform zeroing function.
+	*
+	* NOTE:
+	* SecureZeroMemory2 uses volitle function argument
+	* pointers, which is a contested mehtod of compiler
+	* optimization prevention. GNU seems to oppose this method
+	*
+	* https://learn.microsoft.com/en-us/windows/win32/memory/winbase-securezeromemory2
+	*/
+	#define _IMPL_SECURE_ZERO_MEMSET SecureZeroMemory
+#endif /* !_IMPL_SECURE_ZERO_MEMSET */
+
+/*
+* Provide win32 fallback for sha256 digest if needed
+*/
+
+#ifndef _IMPL_CRYPTO_SHA256_DIGEST
+	
+	/* Export function fallack */
+	#define _IMPL_CRYPTO_SHA256_DIGEST			_bcrypt_sha256_digest	
+
+	_IMPLSTB cstatus_t _bcrypt_sha256_digest(const cspan_t* data, sha256_t digestOut32)
+	{
+		cstatus_t result;
+		struct _bcrypt_ctx ctx;
+
+		result = CSTATUS_FAIL;	/* Start in fail state */
+
+		IF_BC_FAIL(_bcInitSha256(&ctx, 0)) goto Exit;
+
+		IF_BC_FAIL(_bcCreate(&ctx)) goto Exit;
+
+		IF_BC_FAIL(_bcHashData(&ctx, data)) goto Exit;
+	
+		IF_BC_FAIL(_bcFinishHash(&ctx, digestOut32)) goto Exit;
+
+		result = CSTATUS_OK;	/* Hash operation completed, so set success */
+
+	Exit:
+
+		_bcDestroyCtx(&ctx);
+
+		return result;
+	}
+
+#endif /* !_IMPL_CRYPTO_SHA256_DIGEST */
+
+#ifndef _IMPL_CRYPTO_SHA256_HMAC
+
+	/* Export function */
+	#define _IMPL_CRYPTO_SHA256_HMAC				_bcrypt_hmac_sha256	
+	
+	_IMPLSTB cstatus_t _bcrypt_hmac_sha256(const cspan_t* key, const cspan_t* data, sha256_t hmacOut32)
+	{
+		cstatus_t result;
+		struct _bcrypt_ctx ctx;
+
+		result = CSTATUS_FAIL;		/* Start in fail state */
+
+		/* Init context with hmac flag set */
+		IF_BC_FAIL(_bcInitSha256(&ctx, BCRYPT_ALG_HANDLE_HMAC_FLAG)) goto Exit;
+
+		IF_BC_FAIL(_bcCreateHmac(&ctx, key)) goto Exit;
+
+		IF_BC_FAIL(_bcHashData(&ctx, data)) goto Exit;
+
+		IF_BC_FAIL(_bcFinishHash(&ctx, hmacOut32)) goto Exit;
+
+		result = CSTATUS_OK;	/* HMAC operation completed, so set success */
+
+	Exit:
+		
+		_bcDestroyCtx(&ctx);
+
+		return result;
+	}
+
+#endif /* !_IMPL_CRYPTO_SHA256_HMAC */
+
+/*
+* Provide a fallback HKDF expand function using the
+* HMAC function as a base.
+*/
+
+#ifndef _IMPL_CRYPTO_SHA256_HKDF_EXPAND
+
+	#define _IMPL_CRYPTO_SHA256_HKDF_EXPAND		_bcrypt_fallback_hkdf_expand
+
+	cstatus_t _bcrypt_hkdf_update(void* ctx, const cspan_t* data)
+	{
+		DEBUG_ASSERT(ctx != NULL)
+
+		BC_FAIL(_bcHashData((struct _bcrypt_ctx*)ctx, data))
+		return CSTATUS_OK;
+	}
+
+	cstatus_t _bcrypt_hkdf_finish(void* ctx, sha256_t hmacOut32)
+	{
+		DEBUG_ASSERT(ctx != NULL)
+
+		BC_FAIL(_bcFinishHash((struct _bcrypt_ctx*)ctx, hmacOut32))
+		return CSTATUS_OK;
+	}
+
+	_IMPLSTB cstatus_t _bcrypt_fallback_hkdf_expand(const cspan_t* prk, const cspan_t* info, span_t* okm)
+	{
+		cstatus_t result;
+		struct _bcrypt_ctx ctx;
+		struct nc_hkdf_fn_cb_struct handler;
+
+		handler.update = _bcrypt_hkdf_update;
+		handler.finish = _bcrypt_hkdf_finish;
+
+		/* Init bcrypt */
+		BC_FAIL(_bcInitSha256(&ctx, BCRYPT_ALG_HANDLE_HMAC_FLAG))
+
+		BC_FAIL(_bcCreateHmac(&ctx, prk))
+
+		/*
+		* NOTE! Hmac reusable flag must be set to allow for multiple
+		* calls to the finish function without losing the context.
+		*/
+
+		result = hkdfExpandProcess(&handler, &ctx, info, okm);
+
+		_bcDestroyCtx(&ctx);
+
+		return result;
+	}
+
+#endif /* !_IMPL_CRYPTO_SHA256_HKDF_EXPAND */
+
+#endif /* _NC_IS_WINDOWS */
\ No newline at end of file
diff --git a/src/crypto/impl/mbedtls.c b/src/crypto/impl/mbedtls.c
new file mode 100644
index 0000000..057e7b4
--- /dev/null
+++ b/src/crypto/impl/mbedtls.c
@@ -0,0 +1,172 @@
+/*
+* Copyright (c) 2024 Vaughn Nugent
+*
+* Package: noscrypt
+* File: mbedtls.c
+*
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public License
+* as published by the Free Software Foundation; either version 2.1
+* of the License, or  (at your option) any later version.
+*
+* This library is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+* Lesser General Public License for more details.
+*
+* You should have received a copy of the GNU Lesser General Public License
+* along with noscrypt. If not, see http://www.gnu.org/licenses/.
+*/
+
+
+/*
+* This file contains implemntation functions for the required 
+* cryptography primitives of noscrypt. This file stubs functionality
+* using the Mbed-TLS library, if the builder desires to link against
+* it. 
+*/
+
+#ifdef MBEDTLS_CRYPTO_LIB
+
+/* Inline errors on linux in header files on linux */
+#ifndef inline
+	#define inline __inline
+#endif
+
+#include <mbedtls/md.h>
+#include <mbedtls/hkdf.h>
+#include <mbedtls/hmac_drbg.h>
+#include <mbedtls/sha256.h>
+#include <mbedtls/chacha20.h>
+#include <mbedtls/constant_time.h>
+
+#ifndef inline
+	#undef inline
+#endif
+
+
+_IMPLSTB const mbedtls_md_info_t* _mbed_sha256_alg(void)
+{
+	const mbedtls_md_info_t* info;
+	/* Get sha256 md info for hdkf operations */
+	info = mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
+	DEBUG_ASSERT2(info != NULL, "Expected SHA256 md info pointer to be valid")
+	return info;
+}
+
+#if SIZE_MAX < UINT64_MAX
+	#define _ssize_guard_int(x) if(x > SIZE_MAX) return 1;
+#else
+	#define _ssize_guard_int(x)
+#endif
+
+#ifndef _IMPL_CHACHA20_CRYPT
+	
+	/* Export chacha20 computation */
+	#define _IMPL_CHACHA20_CRYPT _mbed_chacha20_encrypt	
+
+	_IMPLSTB cstatus_t _mbed_chacha20_encrypt(
+		const uint8_t* key,
+		const uint8_t* nonce,
+		const uint8_t* input,
+		uint8_t* output,
+		uint32_t dataLen
+	)
+	{
+		_overflow_check(dataLen)
+
+		/* Counter always starts at 0 */
+		return mbedtls_chacha20_crypt(
+			key, 
+			nonce, 
+			0x00u,		/* nip-44 counter version */
+			dataLen, 
+			input, 
+			output
+		) == 0 ? CSTATUS_OK : CSTATUS_FAIL;
+	}
+
+#endif
+
+/* Export sha256 if not already defined */
+#ifndef _IMPL_CRYPTO_SHA256_DIGEST	
+	
+	#define _IMPL_CRYPTO_SHA256_DIGEST			_mbed_sha256_digest	
+
+	_IMPLSTB cstatus_t _mbed_sha256_digest(const cspan_t* data, sha256_t digestOut32)
+	{
+		_overflow_check(data->size)
+
+		return mbedtls_sha256(
+			data->data, 
+			data->size, 
+			digestOut32, 
+			0				/* Set 0 for sha256 mode */
+		) == 0 ? CSTATUS_OK : CSTATUS_FAIL;
+	}
+
+#endif
+
+/* Export Sha256 hmac if not already defined by other libs */
+#ifndef _IMPL_CRYPTO_SHA256_HMAC
+
+	#define _IMPL_CRYPTO_SHA256_HMAC			_mbed_sha256_hmac
+
+	_IMPLSTB cstatus_t _mbed_sha256_hmac(const cspan_t* key, const cspan_t* data, sha256_t hmacOut32)
+	{
+		_overflow_check(data->size)
+
+		/* Keys should never be large enough for this to matter, but sanity check. */
+		DEBUG_ASSERT2(key->size < SIZE_MAX, "Expected key size to be less than SIZE_MAX")
+
+		return mbedtls_md_hmac(
+			_mbed_sha256_alg(),
+			key->data, 
+			key->size,
+			data->data, 
+			data->size,
+			hmacOut32
+		) == 0 ? CSTATUS_OK : CSTATUS_FAIL;
+	}
+#endif
+
+/* Export hkdf expand if not already defined */
+#ifndef _IMPL_CRYPTO_SHA256_HKDF_EXPAND
+
+	#define _IMPL_CRYPTO_SHA256_HKDF_EXPAND		_mbed_sha256_hkdf_expand
+
+	_IMPLSTB cstatus_t _mbed_sha256_hkdf_expand(const cspan_t* prk, const cspan_t* info, span_t* okm)
+	{
+		/* These sizes should never be large enough to overflow on <64bit platforms, but sanity check */
+		DEBUG_ASSERT(okm->size < SIZE_MAX)
+		DEBUG_ASSERT(prk->size < SIZE_MAX)
+		DEBUG_ASSERT(info->size < SIZE_MAX)
+
+		return mbedtls_hkdf_expand(
+			_mbed_sha256_alg(),
+			prk->data, 
+			prk->size,
+			info->data, 
+			info->size,
+			okm->data, 
+			okm->size
+		) == 0 ? CSTATUS_OK : CSTATUS_FAIL;
+	}
+
+#endif
+
+/* Export fixed-time compare if not already defined */
+#ifndef _IMPL_CRYPTO_FIXED_TIME_COMPARE
+
+	#define _IMPL_CRYPTO_FIXED_TIME_COMPARE		_mbed_fixed_time_compare
+
+	/* fixed-time memcmp */
+	_IMPLSTB uint32_t _mbed_fixed_time_compare(const uint8_t* a, const uint8_t* b, uint32_t size)
+	{
+		_ssize_guard_int(size)
+
+		return (uint32_t)mbedtls_ct_memcmp(a, b, size);
+	}
+#endif
+
+#endif
\ No newline at end of file
diff --git a/src/crypto/impl/monocypher.c b/src/crypto/impl/monocypher.c
new file mode 100644
index 0000000..7c9faea
--- /dev/null
+++ b/src/crypto/impl/monocypher.c
@@ -0,0 +1,80 @@
+/*
+* Copyright (c) 2024 Vaughn Nugent
+*
+* Package: noscrypt
+* File: impl/monocypher.c
+*
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public License
+* as published by the Free Software Foundation; either version 2.1
+* of the License, or  (at your option) any later version.
+*
+* This library is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+* Lesser General Public License for more details.
+*
+* You should have received a copy of the GNU Lesser General Public License
+* along with noscrypt. If not, see http://www.gnu.org/licenses/.
+*/
+
+
+/*
+*  This file handles some fallbacks that may not be available on 
+*	some platforms. More specifically:
+*		- Secure memset 0
+* 		- Chacha20 cipher
+* 
+*/
+
+#ifdef NC_ENABLE_MONOCYPHER
+
+#include <monocypher.h>
+
+#include "nc-util.h"
+
+/* Export secure memse0 */
+#ifndef _IMPL_SECURE_ZERO_MEMSET
+
+	/* export cytpo wipe function as is */
+	#define _IMPL_SECURE_ZERO_MEMSET crypto_wipe	
+#endif
+
+/* Export Chacha20 */
+#ifndef _IMPL_CHACHA20_CRYPT
+
+	#define _IMPL_CHACHA20_CRYPT _mc_chacha20_crypt
+
+	_IMPLSTB cstatus_t _mc_chacha20_crypt(
+		const uint8_t* key,
+		const uint8_t* nonce,
+		const uint8_t* input,
+		uint8_t* output,
+		uint32_t dataLen
+	)
+	{
+		_overflow_check(dataLen)
+
+		/*
+		* Function returns the next counter value which is not
+		* needed for noscrypt as encryptions are one-shot, and 
+		* require a new nonce for each encryption.
+		* 
+		* ITEF function uses a 12byte nonce which is required for
+		* nip-44 compliant encryption.
+		*/
+		crypto_chacha20_ietf(
+			output,
+			input,
+			(size_t)dataLen,
+			key,
+			nonce,
+			0x00			/* Counter always starts at 0 */
+		);
+
+		return CSTATUS_OK;
+	}
+
+#endif
+
+#endif /* !NC_ENABLE_MONOCYPHER */
\ No newline at end of file
diff --git a/src/crypto/impl/openssl.c b/src/crypto/impl/openssl.c
new file mode 100644
index 0000000..fd3b4e6
--- /dev/null
+++ b/src/crypto/impl/openssl.c
@@ -0,0 +1,180 @@
+/*
+* Copyright (c) 2024 Vaughn Nugent
+*
+* Package: noscrypt
+* File: impl/openssl.c
+*
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public License
+* as published by the Free Software Foundation; either version 2.1
+* of the License, or  (at your option) any later version.
+*
+* This library is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+* Lesser General Public License for more details.
+*
+* You should have received a copy of the GNU Lesser General Public License
+* along with noscrypt. If not, see http://www.gnu.org/licenses/.
+*/
+
+
+/* Setup openssl */
+#ifdef OPENSSL_CRYPTO_LIB
+
+#include "nc-util.h"
+#include <openssl/crypto.h>
+
+#define _OSSL_FAIL(x) if(!(x)) return CSTATUS_FAIL;
+
+#ifndef _IMPL_SECURE_ZERO_MEMSET
+
+	#define _IMPL_SECURE_ZERO_MEMSET			_ossl_secure_zero_memset
+
+	_IMPLSTB void _ossl_secure_zero_memset(void* ptr, size_t size)
+	{
+		_overflow_check(size)
+
+		OPENSSL_cleanse(ptr, size);
+	}
+#endif
+
+#ifndef _IMPL_CRYPTO_FIXED_TIME_COMPARE
+
+	#define _IMPL_CRYPTO_FIXED_TIME_COMPARE		_ossl_fixed_time_compare
+
+	_IMPLSTB uint32_t _ossl_fixed_time_compare(const uint8_t* a, const uint8_t* b, uint32_t size)
+	{
+		int result;
+
+		/* Size checks are required for platforms that have integer sizes under 32bit */
+		_overflow_check(size)
+
+		result = CRYPTO_memcmp(a, b, size);
+
+		return (uint32_t)result;
+	}
+
+#endif /* _IMPL_CRYPTO_FIXED_TIME_COMPARE */
+
+
+#ifndef _IMPL_CRYPTO_SHA256_DIGEST	
+
+	#include <openssl/sha.h>
+
+	#define _IMPL_CRYPTO_SHA256_DIGEST			_ossl_sha256_digest	
+
+	_IMPLSTB cstatus_t _ossl_sha256_digest(const cspan_t* data, sha256_t digestOut32)
+	{
+		_overflow_check(data->size)
+
+		_OSSL_FAIL(SHA256(data->data, data->size, digestOut32))
+
+		return CSTATUS_OK;
+	}
+
+#endif
+
+#ifndef _IMPL_CRYPTO_SHA256_HMAC
+
+	#include <openssl/hmac.h>
+
+	/* Export function */
+	#define _IMPL_CRYPTO_SHA256_HMAC			_ossl_hmac_sha256	
+	
+	_IMPLSTB cstatus_t _ossl_hmac_sha256(const cspan_t* key, const cspan_t* data, sha256_t hmacOut32)
+	{
+		unsigned int hmacLen;
+
+		_overflow_check(key->size)
+		_overflow_check(data->size)
+
+		hmacLen = sizeof(sha256_t);
+
+		_OSSL_FAIL(
+			HMAC(
+				EVP_sha256(),
+				key->data,
+				key->size,
+				data->data,
+				data->size,
+				hmacOut32,
+				&hmacLen
+			)
+		)
+		
+		/* digest length should match the actual digest size */
+		DEBUG_ASSERT(hmacLen == sizeof(sha256_t))
+
+		return CSTATUS_OK;
+	}
+
+#endif /* !_IMPL_CRYPTO_SHA256_HMAC */
+
+#ifndef _IMPL_CRYPTO_SHA256_HKDF_EXPAND
+	
+	#include <openssl/hmac.h>
+	#include "hkdf.h"
+
+	#define _IMPL_CRYPTO_SHA256_HKDF_EXPAND		_ossl_sha256_hkdf_expand
+
+	cstatus_t _ossl_hkdf_update(void* ctx, const cspan_t* data)
+	{
+		DEBUG_ASSERT(ctx != NULL)
+
+		_overflow_check(data->size)
+
+		_OSSL_FAIL(EVP_DigestUpdate((EVP_MD_CTX*)ctx, data->data, data->size))
+		
+		return CSTATUS_OK;
+	}
+
+	cstatus_t _ossl_hkdf_finish(void* ctx, sha256_t hmacOut32)
+	{
+		unsigned int hmacSize;
+
+		DEBUG_ASSERT(ctx != NULL)
+
+		hmacSize = sizeof(sha256_t);
+
+		_OSSL_FAIL(EVP_DigestFinal_ex((EVP_MD_CTX*)ctx, hmacOut32, &hmacSize))
+
+		/* When configured for sha256, should always be the same size in/out */
+		DEBUG_ASSERT(hmacSize == sizeof(sha256_t))
+		
+		return CSTATUS_OK;
+	}
+
+	_IMPLSTB cstatus_t _ossl_sha256_hkdf_expand(const cspan_t* prk, const cspan_t* info, span_t* okm)
+	{
+		EVP_MD_CTX* ctx;
+		cstatus_t result;
+		struct nc_hkdf_fn_cb_struct handler;
+	
+		/*
+		* NOTE! Hmac reusable flag must be set to allow for multiple
+		* calls to the finish function without losing the context.
+		*/
+
+		if ((ctx = EVP_MD_CTX_create()) == NULL)
+		{
+			return CSTATUS_FAIL;
+		}
+
+		_OSSL_FAIL(EVP_DigestInit_ex2(ctx, EVP_sha256(), NULL))
+
+		_OSSL_FAIL(EVP_DigestUpdate(ctx, prk->data, prk->size));
+		
+		handler.update = _ossl_hkdf_update;
+		handler.finish = _ossl_hkdf_finish;
+
+		result = hkdfExpandProcess(&handler, ctx, info, okm);
+
+		EVP_MD_CTX_destroy(ctx);
+
+		return result;
+	}
+
+#endif /* !_IMPL_CRYPTO_SHA256_HKDF_EXPAND */
+
+#endif	/*!OPENSSL_CRYPTO_LIB */
\ No newline at end of file
diff --git a/src/crypto/nc-crypto.c b/src/crypto/nc-crypto.c
new file mode 100644
index 0000000..587d59d
--- /dev/null
+++ b/src/crypto/nc-crypto.c
@@ -0,0 +1,283 @@
+/*
+* Copyright (c) 2024 Vaughn Nugent
+*
+* Package: noscrypt
+* File: nc-crypto.c
+*
+* This library is free software; you can redistribute it and/or
+* modify it under the terms of the GNU Lesser General Public License
+* as published by the Free Software Foundation; either version 2.1
+* of the License, or  (at your option) any later version.
+*
+* This library is distributed in the hope that it will be useful,
+* but WITHOUT ANY WARRANTY; without even the implied warranty of
+* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+* Lesser General Public License for more details.
+*
+* You should have received a copy of the GNU Lesser General Public License
+* along with noscrypt. If not, see http://www.gnu.org/licenses/.
+*/
+
+#include "nc-util.h"
+#include "nc-crypto.h"
+
+/*
+*  Functions are not forced inline, just suggested.
+*  So unless it becomes a performance issue, I will leave
+*  most/all impl functions inline and let the compiler 
+*  decide.
+*/
+
+#define _IMPLSTB static _nc_fn_inline
+
+/*
+* Impl .c files may define the following macros for function implementations:
+* 
+*		_IMPL_SECURE_ZERO_MEMSET			secure memset 0 function
+*		_IMPL_CHACHA20_CRYPT				chacha20 cipher function
+*		_IMPL_CRYPTO_FIXED_TIME_COMPARE		fixed time compare function
+*		_IMPL_CRYPTO_SHA256_HMAC			sha256 hmac function
+*		_IMPL_CRYPTO_SHA256_DIGEST			standard sha256 digest function
+* 		_IMPL_CRYPTO_SHA256_HKDF_EXPAND		hkdf expand function
+* 		_IMPL_CRYPTO_SHA256_HKDF_EXTRACT	hkdf extract function
+* 
+* Macros are used to allow the preprocessor to select the correct implementation
+* or raise errors if no implementation is defined.
+* 
+* Implementation functions can assume inputs have been checked/sanitized by the
+* calling function, and should return CSTATUS_OK on success, CSTATUS_FAIL on failure.
+*/
+
+
+/*
+* Prioritize embedded builds with mbedtls
+*/
+#include "impl/mbedtls.c"
+
+/*
+* Include openssl as an alternative default 
+* implementation
+*/
+#include "impl/openssl.c"
+
+/*
+* Include win32 platform specific fallback support 
+* using bcrypt.
+*/
+#include "impl/bcrypt.c"
+
+/*
+* Handle default implementations of secure 
+* memset 0 functions for each platform.
+*/
+#ifndef _IMPL_SECURE_ZERO_MEMSET
+   /* only incude bzero if libc version greater than 2.25 */
+	#if defined(__GLIBC__) && defined(__GLIBC_MINOR__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 25
+		/*
+		*	When using libc, we can use explicit_bzero
+		*	as secure memset implementation.
+		* 
+		*	https://sourceware.org/glibc/manual/2.39/html_mono/libc.html#Erasing-Sensitive-Data
+		*/
+		#include <string.h>
+		extern void explicit_bzero(void* block, size_t len);
+		#define _IMPL_SECURE_ZERO_MEMSET explicit_bzero
+	#endif
+#endif
+
+/*
+* Finally fall back to monocipher to handle some
+* that are not provided by other libraries.
+*
+* Platform specific opimizations are considered
+* "better" than monocypher options, so this is
+* added as a last resort. Momocypher is "correct"
+* and portable, but not optimized for any specific
+* platform.
+*/
+#include "impl/monocypher.c"
+
+
+#ifdef _IMPL_CRYPTO_SHA256_HMAC
+
+	/*
+	* If a library does not provide a HKDF extract function,
+	* we can just use the HMAC function as a fallback.
+	*
+	* This is a fallback because another library may provide
+	* a more optimized implementation.
+	*/
+
+	#ifndef _IMPL_CRYPTO_SHA256_HKDF_EXTRACT 
+
+		#define _IMPL_CRYPTO_SHA256_HKDF_EXTRACT		_fallbackHkdfExtract
+
+		_IMPLSTB cstatus_t _fallbackHkdfExtract(const cspan_t* salt, const cspan_t* ikm, sha256_t prk)
+		{
+			return _IMPL_CRYPTO_SHA256_HMAC(salt, ikm, prk);
+		}
+
+	#endif /* !_IMPL_CRYPTO_SHA256_HKDF_EXTRACT */
+	
+#endif /* _IMPL_CRYPTO_SHA256_HMAC */
+
+/* Fallback for fixed time comparison for all platforms */
+#ifndef _IMPL_CRYPTO_FIXED_TIME_COMPARE
+
+	#pragma message("Warning: No fixed time compare implementation defined, using fallback. This may not be secure on all platforms")
+
+	#define _IMPL_CRYPTO_FIXED_TIME_COMPARE	_fallbackFixedTimeCompare
+
+	/*
+	* This implemntation is a slightly simplified version of 
+	* MBed TLS constant time memcmp function, knowm to be a 32bit 
+	* integer size
+	*/
+
+	static uint32_t _fallbackFixedTimeCompare(const uint8_t* a, const uint8_t* b, uint32_t size)
+	{
+		size_t i;
+		uint32_t result;
+		uint8_t O;
+		volatile const uint8_t* A, * B;		
+
+		result = 0;
+		O = 0;
+		A = (volatile const uint8_t*)a;
+		B = (volatile const uint8_t*)b;
+
+		/* Compare each byte */
+		for(i = 0; i < size; i++)
+		{
+			/* Handle volatile read */
+			O |= (A[i] ^ B[i]);
+
+			result |= O;
+		}
+
+		return result;
+	}
+
+#endif /* !_IMPL_CRYPTO_FIXED_TIME_COMPARE */
+
+
+/*
+* Internal function implementations that perform
+* basic checking and call the correct implementation
+* for the desired crypto impl.
+* 
+* The following functions MUST be assumed to 
+* perform basic input validation. Since these apis are 
+* internal, debug asserts are used to ensure the
+* function has been used correctly.
+*/
+
+void ncCryptoSecureZero(void* ptr, uint32_t size)
+{
+	DEBUG_ASSERT2(ptr != NULL, "Expected ptr to be non-null")
+
+#ifndef _IMPL_SECURE_ZERO_MEMSET
+	#error "No secure memset implementation defined"
+#endif /* _IMPL_SECURE_ZERO_MEMSET */
+
+	_IMPL_SECURE_ZERO_MEMSET(ptr, size);
+}
+
+uint32_t ncCryptoFixedTimeComp(const uint8_t* a, const uint8_t* b, uint32_t size)
+{
+	DEBUG_ASSERT2(a != NULL, "Expected a to be non-null")
+	DEBUG_ASSERT2(b != NULL, "Expected b to be non-null")
+
+#ifndef _IMPL_CRYPTO_FIXED_TIME_COMPARE
+	#error "No fixed time compare implementation defined"
+#endif /* !_IMPL_CRYPTO_FIXED_TIME_COMPARE */
+
+	return _IMPL_CRYPTO_FIXED_TIME_COMPARE(a, b, size);
+}
+
+cstatus_t ncCryptoDigestSha256(const cspan_t* data, sha256_t digestOut32)
+{
+	/* Debug arg validate */
+	DEBUG_ASSERT2(data != NULL && data->data != NULL,	"Expected data to be non-null")
+	DEBUG_ASSERT2(digestOut32 != NULL,					"Expected digestOut32 to be non-null")
+
+#ifndef _IMPL_CRYPTO_SHA256_DIGEST
+	#error "No SHA256 implementation defined"
+#endif /* !_IMPL_CRYPTO_SHA256_DIGEST */
+
+	return _IMPL_CRYPTO_SHA256_DIGEST(data, digestOut32);
+}
+
+cstatus_t ncCryptoHmacSha256(const cspan_t* key, const cspan_t* data, sha256_t hmacOut32)
+{
+	/* Debug arg validate */
+	DEBUG_ASSERT2(key != NULL && key->data != NULL,			"Expected key to be non-null")
+	DEBUG_ASSERT2(data != NULL && data->data != NULL,		"Expected data to be non-null")
+	DEBUG_ASSERT2(hmacOut32 != NULL && data->data != NULL,	"Expected hmacOut32 to be non-null")
+
+#ifndef _IMPL_CRYPTO_SHA256_HMAC
+	#error "No SHA256 HMAC implementation defined"
+#endif /* !_IMPL_CRYPTO_SHA256_HMAC */
+
+	return _IMPL_CRYPTO_SHA256_HMAC(key, data, hmacOut32);
+}
+
+cstatus_t ncCryptoSha256HkdfExpand(const cspan_t* prk, const cspan_t* info, span_t* okm)
+{
+	/* Debug arg validate */
+	DEBUG_ASSERT2(prk != NULL && prk->data != NULL,		"Expected prk to be non-null")
+	DEBUG_ASSERT2(info != NULL && info->data != NULL,	"Expected info to be non-null")
+	DEBUG_ASSERT2(okm != NULL && okm->data != NULL,		"Expected okm to be non-null")
+
+	/*
+	* RFC 5869: 2.3
+	* "length of output keying material in octets (<= 255 * HashLen)"
+	* 
+	* important as the counter is 1 byte, so it cannot overflow
+	*/
+
+	if(okm->size > (uint32_t)(0xFFu * SHA256_DIGEST_SIZE))
+	{
+		return CSTATUS_FAIL;
+	}
+
+#ifndef _IMPL_CRYPTO_SHA256_HKDF_EXPAND
+	#error "No SHA256 HKDF expand implementation defined"
+#endif /* !_IMPL_CRYPTO_SHA256_HKDF_EXPAND */
+	
+	return _IMPL_CRYPTO_SHA256_HKDF_EXPAND(prk, info, okm);
+}
+
+cstatus_t ncCryptoSha256HkdfExtract(const cspan_t* salt, const cspan_t* ikm, sha256_t prk)
+{
+	/* Debug arg validate */
+	DEBUG_ASSERT2(salt != NULL, "Expected salt to be non-null")
+	DEBUG_ASSERT2(ikm  != NULL, "Expected ikm to be non-null")
+	DEBUG_ASSERT2(prk  != NULL, "Expected prk to be non-null")
+
+#ifndef _IMPL_CRYPTO_SHA256_HKDF_EXTRACT
+	#error "No SHA256 HKDF extract implementation defined"
+#endif /* !_IMPL_CRYPTO_SHA256_HKDF_EXTRACT */
+	
+	return _IMPL_CRYPTO_SHA256_HKDF_EXTRACT(salt, ikm, prk);
+}
+
+cstatus_t ncCryptoChacha20(
+	const uint8_t key[CHACHA_KEY_SIZE],
+	const uint8_t nonce[CHACHA_NONCE_SIZE],
+	const uint8_t* input,
+	uint8_t* output,
+	uint32_t dataSize
+)
+{
+	DEBUG_ASSERT2(key != NULL,		"Expected key to be non-null")
+	DEBUG_ASSERT2(nonce != NULL,	"Expected nonce to be non-null")
+	DEBUG_ASSERT2(input != NULL,	"Expected input to be non-null")
+	DEBUG_ASSERT2(output != NULL,	"Expected output to be non-null")
+
+#ifndef _IMPL_CHACHA20_CRYPT
+	#error "No chacha20 implementation defined"
+#endif /* !_IMPL_CHACHA20_CRYPT */
+
+	return _IMPL_CHACHA20_CRYPT(key, nonce, input, output, dataSize);
+}