I do this, minus the "dedicated computer and printer" part. Pretty simple, really. Another option is dedicated smartcards that hold the keys. I'm genuinely cur

I do this, minus the "dedicated computer and printer" part. Pretty simple, really. Another option is dedicated smartcards that hold the keys. I'm genuinely curious. Can you envision any possible distributed internet currency that wouldn't require human interaction for the highest level of security? Keep in mind, the threat model here is someone gaining read access to a few kb of data. With an automated, internet-facing system, I see an airgap as the only reasonable defense against that threat. If someone gains read access to, say, your bank session cookies, they could also feasibly clean you out. The only difference is the bank might be able to reverse the transaction (undesirable a decentralized currency) or cover your losses (not a bad idea).