I was reading about Markov Chain Monte Carlo (MCMC) recently and discovered a very famous application of using them to decrypt substitution ciphers. This blog is meant to serve as notes on how the problem can be framed as a Markov chain and how a simple yet smart Monte Carlo sampling approach can help solve it very efficiently. In this blog post, I won’t be explaining what Markov process and MCMC is, however I’ll add some references for that at the end of this post.