Wandering around maze known as the Computer Science building at Oxford I found the computer science library. Rarely these days do you see a library (and a librarian) devoted to computer science. The librarian found their copy of The Golden Ticket and asked me to inscribe and sign it, just like at Dagstuhl, perhaps the only other active CS library I know of.

It brought back memories of the early 90s when I would often head to the Math/CS library at the University of Chicago to track down some conference or journal paper. Now we just click and download but you miss finding something else interesting in the proceedings or the stacks in general.

I had time to kill so I wandered around the library finding memories in the stacks including the 1987 STOC Proceedings, home to my first conference paper, The complexity of perfect zero-knowledge. The paper might be best known for my upper bound protocol which is republished here in its entirety.

That’s how I wrote it nearly four decades ago, without proof just an intuition why it works. Those were the days. I did work out the full covariance argument in the journal version though I missed other bugs in the proof.

The upper bound requires the verifier to have a random sample of the distribution unknown to the prover. Rahul Santhanam, who is hosting my visit to Oxford, asked if the converse was known. Goldreich, Vadhan and Wigderson, in the appendix of their Laconic Prover paper, show a sampling protocol based on the upper bound on the size of a set, though the sample is not completely unknown to the prover. Neat to revisit questions from my first conference paper.