Let’s say a person is in danger of being kidnaped, or put in jail. Before going in he memorizes a number of pass phrases such as:
“here is an account with 100 btc”
“here is a different account, with 1000 btc”
“this is my ransom account with 5000 btc in it”
“this is my nest egg account with all my money”
“I’ll pay you this passphrase in advance”
“and I’ll pay you this passphrase once I’m out”
(these are bad passphrases, just examples)
He computes the public addresses of these phrases using the process discussed here:https://forum.bitcoin.org/index.php?topic=28877.0
He then memorizes the firstbits for each public address, and transfers bitcoins into them.
Once captured or imprisoned he can still receive money, show the balance of each account (but not prove he controls them), and pay the entire balance of any account to someone without any access to a computer.
He can even confirm he has been paid into an account if he is allowed to call random phone numbers until he reaches someone who will go to http://blockexplorer.com/
and read off the balance of one of the firstbits accounts (anyone known to him or the captor is unreliable).
If he has enough accounts memorized he can even conduct some amount of business, paying and being paid, receiving ‘change’ etc.
And, of course, any accounts that he does not give away still have the money when he gets out.
Granted if people knew you had a ThoughtCoin account then you’d be incentivizing kidnapping weirdly becoming the hostage and the payment, and helping people in jail bribe their way out is probably not a good thing. But it makes me wonder what else could you do with ThoughtCoins. For example, what would be the minimum set of crypto primitives you’d have to memorize to be able to generate your own public keys or transactions with only say pin and paper or a calculator. Would sha256 be enough?