In short, it uses the sum of log probabilities of quadgrams and compares the sum with the sum for the "normal" English text (created as the sum of log probabilities of the most often English quadgrams). and all data download, script, or API access for "Transposition Cipher" are not public, same for offline use on PC, mobile, tablet, iPhone or Android app! Chillotti, I., Gama, N., Georgieva, M. and Izabachne, M. TFHE: Fast fully homomorphic encryption library, Aug. 2016; https://tfhe.github.io/tfhe/. Algorithm Source message Encoded message