Squashed commit of the following:

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

1 files changed, 84 insertions, 2 deletions

diff --git a/src/noscrypt.h b/src/noscrypt.h
index f6bfe76..f7265ad 100644
--- a/src/noscrypt.h
+++ b/src/noscrypt.h
@@ -72,6 +72,8 @@
 #define NC_PUBKEY_SIZE 32
 #define NC_SHARED_SEC_SIZE 32
 #define NC_CONV_KEY_SIZE 32
+#define NC_HMAC_KEY_SIZE 32
+#define NC_ENCRYPTION_MAC_SIZE 32
 #define NC_MESSAGE_KEY_SIZE NIP44_MESSAGE_KEY_SIZE
 
 /*
@@ -80,8 +82,6 @@
 */
 #define NIP44_MIN_ENC_MESSAGE_SIZE 1
 #define NIP44_MAX_ENC_MESSAGE_SIZE 65535
-#define NIP44_MIN_DEC_MESSAGE_SIZE 99
-#define NIP44_MAX_DEC_MESSAGE_SIZE 65603 
 
 /*
 * The Nip44 constant salt 
@@ -169,14 +169,45 @@ typedef struct nc_encryption_struct {
 } NCCryptoData;
 
 /*
+* A structure for Nip44 message authentication code verification. This structure
+* is used to pass arguments to the NCVerifyMac and NCVerifyMacEx functions. 
+*/
+typedef struct nc_mac_verify {
+
+	/* The message authentication code certifying the Nip44 payload */
+	uint8_t mac[NC_ENCRYPTION_MAC_SIZE];
+
+	/* The nonce used for the original message encryption */
+	uint8_t nonce[NC_ENCRYPTION_NONCE_SIZE];
+
+	/* The message payload data */
+	const uint8_t* payload;
+
+	/* The size of the payload data */
+	size_t payloadSize;
+
+} NCMacVerifyArgs;
+
+
+/*
 	API FUNCTIONS
 */
 
+/*
+* A helper function to cast a 32byte buffer to a NCSecretKey struct
+* @param key The 32byte buffer to cast
+* @return A pointer to the NCSecretKey struct
+*/
 static inline NCSecretKey* NCToSecKey(uint8_t key[NC_SEC_KEY_SIZE])
 {
 	return (NCSecretKey*)key;
 }
 
+/*
+* A helper function to cast a 32byte buffer to a NCPublicKey struct
+* @param key The 32byte buffer to cast
+* @return A pointer to the NCPublicKey struct
+*/
 static inline NCPublicKey* NCToPubKey(uint8_t key[NC_PUBKEY_SIZE])
 {
 	return (NCPublicKey*)key;
@@ -377,6 +408,7 @@ NC_EXPORT NCResult NC_CC NCEncrypt(
 	const NCContext* ctx, 
 	const NCSecretKey* sk, 
 	const NCPublicKey* pk, 
+	uint8_t hmacKeyOut[NC_HMAC_KEY_SIZE],
 	NCCryptoData* args
 );
 
@@ -397,6 +429,22 @@ NC_EXPORT NCResult NC_CC NCDecrypt(
 	NCCryptoData* args
 );
 
+/*
+* High level api for verifying a Nip44 message authentication code using a secret key 
+and a public key. Use the NCVerifyMacEx functions for extended verification functionality.
+* @param ctx A pointer to an existing library context
+* @param sk A pointer to the secret key
+* @param pk A pointer to the 32byte compressed public key (x-only serialized public key)
+* @param args A pointer to the mac verification arguments
+* @return NC_SUCCESS if the operation was successful, otherwise an error code. Use NCParseErrorCode to
+* the error code and positional argument that caused the error
+*/
+NC_EXPORT NCResult NC_CC NCVerifyMac(
+	const NCContext* ctx,
+	const NCSecretKey* sk,
+	const NCPublicKey* pk,
+	NCMacVerifyArgs* args
+);
 
 /*--------------------------------------
 *		EXTENDED ENCRYPTION API
@@ -462,6 +510,7 @@ the error code and positional argument that caused the error.
 NC_EXPORT NCResult NC_CC NCEncryptEx(
 	const NCContext* ctx, 
 	const uint8_t conversationKey[NC_CONV_KEY_SIZE],
+	uint8_t hmacKeyOut[NC_HMAC_KEY_SIZE],
 	NCCryptoData* args
 );
 
@@ -480,4 +529,37 @@ NC_EXPORT NCResult NC_CC NCDecryptEx(
 	NCCryptoData* args
 );
 
+/*
+* Verifies a Nip44 message authentication code using the given conversation key.
+* @param ctx A pointer to the existing library context
+* @param conversationKey A pointer to the 32byte conversation key
+* @param args A pointer to the mac verification arguments
+* @return NC_SUCCESS if the operation was successful, otherwise an error code. Use NCParseErrorCode to
+* the error code and positional argument that caused the error.
+*/
+NC_EXPORT NCResult NC_CC NCVerifyMacEx(
+	const NCContext* ctx,
+	const uint8_t conversationKey[NC_CONV_KEY_SIZE],
+	NCMacVerifyArgs* args
+);
+
+/*
+* Computes a message authentication code for a given payload using the given hmacKey and writes the
+* mac to the hmacOut buffer.
+* @param ctx A pointer to the existing library context
+* @param hmacKey A pointer to the 32byte hmac key
+* @param payload A pointer to the payload data buffer
+* @param payloadSize The size of the payload data buffer
+* @param hmacOut A pointer to the 32byte buffer to write the mac to
+* @return NC_SUCCESS if the operation was successful, otherwise an error code. Use NCParseErrorCode to
+* the error code and positional argument that caused the error.
+*/
+NC_EXPORT NCResult NCComputeMac(
+	const NCContext* ctx,
+	const uint8_t hmacKey[NC_HMAC_KEY_SIZE],
+	const uint8_t* payload,
+	size_t payloadSize,
+	uint8_t hmacOut[NC_ENCRYPTION_MAC_SIZE]
+);
+
 #endif // !NOSCRYPT_H