Bill Buchanan - Why Is AES GCM Good (and Not So Good) for Cybersecurity

We live in a strange world of cybersecurity. An auditor might ask a company if they encrypt their data? And the company may reply that they do, and so the auditor would tick that off. But encryption does not just involve the privacy of data; it also involves integrity checking and setting up digital trust. Along with this, there are many ways to implement methods, including key derivation, public key integration, hashing methods, and encryption modes. And, so, last week I outlined how some AES modes can be easily modified.

And so, someone asked me why I recommended GCM (Galois Counter Mode)? Well, GCM integrates integrity into the cipher. It is built on CTR (Counter) mode and is a stream cipher. This makes it fast. Along with this, we can add additional data into the ciphertext — and which defends against playback attacks. At the core of this is the Galois Message Authentication Code (GMAC).