Bibliography of cryptography

At least one work by Trithemius was banned by the Catholic Church and put on the Index Librorum Prohibitorum as being about black magic or witchcraft.

In the 19th century, the general standard improved somewhat (e.g., works by Auguste Kerckhoffs, Friedrich Kasiski, and Étienne Bazeries).

Colonel Parker Hitt and William Friedman in the early 20th century also wrote books on cryptography.

With the invention of radio, much of military communications went wireless, allowing the possibility of enemy interception much more readily than tapping into a landline.

In the US military, mere possession of a copy by cryptographic personnel was grounds for some considerable suspicion[citation needed].