I heard a story somewhere that public key cryptography was known to the NSA long before the 70s. Maybe they are 30 years ahead in cryptographic number theory? Maybe prime factorization isn't actually hard? Maybe...
What was essentially RSA was known to Britain's GCHQ (Government Communications Headquarters) in 1973. Is this what you were thinking of? Rivest, Shamir and Adleman rediscovered it in 1977.
