[kadoban]

> … or was there a quantum computer somewhere and it was just kept hush hush, hence the push for PQ?

If there were a quantum computer somewhere, or close to one, it would be reasonably likely for it to be secret.

I look at the history of crypto in the mid to late 20th century for example. Small groups in the Allies and the NSA and etc. had certainly more knowledge than was public by a wide margin, years to decades.

[charlieyu1]

By 1990s they were pretty rubbish. DES could be cracked by home PCs for a couple of days.

[thombat]

That's not quite correct. The first (public) brute-forcing of DES was done in 1997 by the DESCHALL project distributing the search across tens of thousands of volunteer's computers for weeks [1]. The EFF then spent $250,000 to build a dedicated DES cracker ("Deep Crack") which required an average of four days per key found [2]

[1] https://en.m.wikipedia.org/wiki/DESCHALL_Project

[2] https://en.m.wikipedia.org/wiki/EFF_DES_cracker

[kadoban]

DES itself is an example of the NSA being ahead of the field. The designed the S-box to be resistant against attacks nobody knew about yet.

Like the sibling comment points out, you're overstating the weakness of DES as well.