strncmp -> memcmp, fix typo in error message Ivalid -> Invalid, add printing for invalid MAC error.
strncmp -> memcmp, fix typo in error message Ivalid -> Invalid, add printing for invalid MAC error.

iotauth/iotauth,iotauth/iotauth,iotauth/iotauth,iotauth/iotauth,iotauth/iotauth,iotauth/iotauth