You keep saying "the Galois Field" as if that was a thing. It's GCM. The components of GCM are CTR mode and the GMAC authentication code, which is based on GHASH. If you're afraid of Galois fields, you don't get to use AES at all! Nobody should be implementing any of these primitives themselves, very much including CBC, which, as you saw downthread, left both you and the author of this project with an insecure cryptosystem.
Vulnerabilities in CBC systems were for a long time during the 2000s the most common crypto vulnerabilities on the Internet. There are more things that go wrong with CBC mode than just forgetting to authenticate it!
Vulnerabilities in CBC systems were for a long time during the 2000s the most common crypto vulnerabilities on the Internet. There are more things that go wrong with CBC mode than just forgetting to authenticate it!