TxtCipher code review: RC4 keystream reuse and a versioned AES format AI;DR – The security review described here was done by Claude Code with the Fable model, and the resulting changes and this blog post were developed with significant help from it. If you don’t want to read “AI slop”, stop reading now. TxtCipher is a small web page that encrypts and decrypts text with a password. I wrote it to exchange text with TxtCrypt, a macOS pr https://blog.dummzeuch.de/2026/09/15/txtcipher-code-review-rc4-keystream-reuse-and-a-versioned-aes-format/ #AI