I don't want to see a specific keyword; all I'm saying is that there is nothing on that website indicating any great knowledge of theoretical cryptography. For instance: no proofs, formal definitions, nothing. Not even links to other websites hosting such things.
I really feel frustrated by your lack of search/manual-crawling/link-clicking/understanding capabilities. He was the official security reviewer of Bitcoin and Ethereum. Then some extra references so you can continue your own search:
I am not doubting Sergio's security expertise, but security expertise != theoretical cryptography expertise. Crypto requires providing clear definitions and proofs of security. All I see in the first two links are adhoc constructions, with heuristic arguments for security; no security definitions, no reductions, no proofs.
The last link is more formal, and talks about models of computation, but once again does not provide any reductions.
