Before the modern era, cryptography was concerned solely with message confidentiality (i.e., encryption)—conversion of messages from a comprehensible form into an incomprehensible one and back again at the other end, rendering it unreadable by interceptors or eavesdroppers without secret knowledge (namely the key needed for decryption of that message).
Encryption attempted to ensure secrecy in communications, such as those of spies, military leaders, and diplomats. In recent decades, the field has expanded beyond confidentiality concerns to include techniques for message integrity checking, sender/receiver identity authentication, digital signatures, interactive proofs and secure computation, among others.
Below, you will find the declassified FBI File that was labeled “Cryptography.”
The file stretches back to the mid to late 1930s! It is an ongoing FOIA request, wherein many documents have not been released yet, and are being reviewed by multiple agencies. I will continue to add the releases, as they become available.
Federal Bureau of Investigation (FBI) Release
Federal Bureau of Investigation (FBI) Release #1, October 19, 2016 [356 Pages, 190.5MB]
United States Army Release, November 17, 2016 [34 Pages, 4.9MB]