Merge branch 'gg/enhancement/add_sender_hmac_to_message_v2' of https://github.com/xmtp/xmtp-android into gg/enhancement/add_sender_hmac_to_message_v2

Author: nplasterer

library/src/main/java/org/xmtp/android/library/Crypto.kt

@@ -87,10 +87,9 @@ class Crypto {
 
         fun deriveKey(
             secret: ByteArray,
-            salt: ByteArray,
             info: ByteArray,
         ): ByteArray {
-            val derivationParameters = HKDFParameters(secret, salt, info)
+            val derivationParameters = HKDFParameters(secret, ByteArray(0), info)
             val digest = SHA256Digest()
             val hkdfGenerator = HKDFBytesGenerator(digest)
             hkdfGenerator.init(derivationParameters)
@@ -104,8 +103,8 @@ class Crypto {
             info: ByteArray,
             message: ByteArray,
         ): ByteArray {
-            val hkdfKey = deriveKey(secret, message, info)
-            return calculateMac(secret, hkdfKey)
+            val hkdfKey = deriveKey(secret, info)
+            return calculateMac(hkdfKey, message)
         }
     }
 }