PUBLIC RESEARCH / SOURCE GUIDE
Cryptology and Declassified NSA History
Cryptography, signals intelligence and public historical records.
Quick answer
What declassified NSA history is public?
The National Security Agency, created on November 4, 1952, publishes declassified histories through its Center for Cryptologic History and runs the National Cryptologic Museum. Major releases include the Venona decrypts of Soviet messages, made public in 1995, and an internal study, declassified in 2005, concluding that the second Gulf of Tonkin attack in August 1964 did not happen.
Start with the original record
Distinguish historical cryptology from fictional terminal missions and real-world intrusion.
How to investigate
- Locate the original record and note its author, date and archive identifier.
- Separate what the record states from what later commentators infer.
- Cross-check the claim with independent documents and contemporaneous reporting.
- Record what remains unknown or disputed.
This page is an orientation guide, not an assertion that any specific conspiracy claim is established. The linked official source is an entry point; individual documents have not been exhaustively verified.
Continue your investigation
Key facts and dates
- November 4, 1952: The NSA is established.
- 1943 to 1980: The Venona project decrypts Soviet intelligence messages. The files are released in 1995.
- 1993: The National Cryptologic Museum opens near Fort Meade, Maryland.
- 2005: The NSA declassifies historian Robert Hanyok's study concluding that no North Vietnamese attack occurred on August 4, 1964.
- The Center for Cryptologic History publishes many declassified histories free online.
Common questions
Did the Gulf of Tonkin attack really happen?
The first clash on August 2, 1964 did happen. The NSA's own historian concluded that the reported second attack on August 4, which was used to justify escalating the Vietnam War, did not occur.
What was Venona?
Venona was a US program that decrypted Soviet intelligence messages sent during the 1940s. It exposed Soviet spying in the United States and stayed secret until 1995.
Can you visit the NSA museum?
Yes. The National Cryptologic Museum near Fort Meade, Maryland is open to the public and free.
Stories built on this record
The files below start from this record. Then they keep going. The first pages of every file are free.
Last reviewed 2026-10-13. Facts on this page come from the official sources linked above and the published record. Archive files are dramatized and always marked as files.