Book ciphers would make sense to use to prevent prying eyes from reading your mail. They’re cumbersome but since they’re one-time pads they’re virtually unbreakable.
24 posted on 05/26/2016 11:37:34 AM PDT by MeganC
(The Republic of The United States of America: 7/4/1776 to 6/26/2015 R.I.P.)