Oddbean

It's a good thing you put "crypto" in quotes, to alert me to look for the intended meaning. You apparently meant "blockchains". For me, "crypto" means the array of symmetric, public key, and hash algorithms that are classified by the US as "munitions" (and thus subject to 2nd amendment protection). These enable signing documents, encrypting documents to a specific pubkey, computing a unique secure handle for a document (ipfs, and other schemes that use hashes in links), authentication without shared secrets (aka passwords), etc, etc Email, usenet, and other social media developed in the 80s - but it was unauthenticated. It was trivial to spoof a usenet article as a joke. Email was flexible enough to incorporate various forms of authentication as an add-on. (Ironically, the original authentication of HELO is often misconfigured and rarely checked.) New protocols incorporate authentication as a MUST and various privacy features as options. So, in my view, the #1 problem crypto solves is authentication. #2 problem is privacy.