How about validating whether a given AS is an acceptable origin for a set of prefixes? Seems like a problem (route hijacking) that's still been looking for a solution. Lots of BGP routers, RRs, prefix databases are around, maintained and generally online. Current practices are incomplete and for many large carriers, operate on a 24 hour cycle which might not be acceptable if the world had a more instant option in place.
It is not my impression that maintaining an updatable database of (AS, prefix) pairs is particularly difficult. What's hard is figuring out who's allowed to put what into the database, and blockchains offer no help at all there. See https://xkcd.com/927/ Regards, John Levine, johnl@iecc.com, Primary Perpetrator of "The Internet for Dummies", Please consider the environment before reading this e-mail. https://jl.ly