Cryptography Basics: Ciphers, Modes, and Tampering
A three-post series on the core ideas behind symmetric encryption, each one built around a real, runnable demo instead of just the math. Post 1 breaks the Caesar cipher by brute force to show why a small keyspace dooms any cipher no matter how the shift is picked. Post 2 encrypts an actual image under AES in ECB and CBC mode to show, visually and by byte count, why a strong cipher still leaks patterns without a proper mode of operation. Post 3 moves from confidentiality to integrity, using AES-GCM to show what authenticated encryption buys you: a tampered ciphertext gets refused instead of silently decrypting into corrupted data.