alt Hacker NewsSymmetric encryption is computationally ~free, but most of them are conceptually complex. The purpose of encryption here isn't security, it's obfuscation in the service of dissuading people from depending on something they shouldn't, so using the absolutely simplest thing that could possibly work is a positive.
XOR with fixed key is trivially figure-out-able, defeating the purpose. Speck is simple enough that a working implementation is included within the wikipedia article, and most LLMs can oneshot it.