The Evolution of Block Ciphers in HTTPS and the Dominance of GCM Mode

This article explains block cipher encryption, focusing on AES and its use with HTTPS to ensure secure communications. AES encrypts fixed-size blocks of data (128, 192, or 256 bits), but for longer data such as emails or HTTPS sessions, modes of operation are needed to encrypt messages larger than one block. The piece reviews several block cipher modes: ECB, considered insecure because it reveals patterns; CBC, which has been vulnerable to padding oracle attacks and is deprecated in TLS 1.3; CTR, which uses a nonce and counter to create a pseudo-random key stream but is unsafe if the nonce is reused; and GCM, the current standard that combines CTR encryption with authentication to guarantee message integrity and authenticity. The article details how GCM adds a MAC tag generated via Galois field operations to detect tampering. It also mentions ChaCha20-Poly1305 as a popular alternative suited for devices lacking hardware acceleration for AES. Overall, the article highlights the historical progression of encryption modes securing HTTPS and why AES-GCM is predominant today due to its security and efficiency.