Can you hear that? A certain high frequency hum which, until recently, was perceptible only to dogs, bats, and cryptography cognoscenti? It’s the mounting buzz over “blockchain”—an umbrella term referring to a number of shared ledger services that promise to revolutionize every aspect of social and political exchange, from financial transactions to medical data, voter registration to birth certificates. Due in large part to the way they address the twinned threats of system failure and malicious users which plague our …