Obviously cryptographers were not naive about future technology. One example that comes to my mind is this: in a 1981 paper discussing Triple DES, the authors s

Obviously cryptographers were not naive about future technology. One example that comes to my mind is this: in a 1981 paper discussing Triple DES, the authors state: “A generalized meet in the middle attack would then require 2^112 operations and be well beyond the foreseeable technology for at least 50 years, and possibly forever.” - Merkle, R. and M. Hellman, "On the Security of Multiple Encryption", Communications of the ACM, vol. 24, no. 7, pp. 465–467, July 1981 While I would not count on any Triple DES encrypted data remaining secret forever, their other prediction has held up for the time being – 2^112 operations is still completely out of reach 43 years later. Of course there are other ways to attack TDES and it is rightfully considered obsolete.