Hardware Bitcoin wallet - a minimal Bitcoin wallet for embedded devices

[emma.lee1890]

**Hardware Bitcoin wallet**  is a project which aims to implement a minimal dedicated Bitcoin wallet. Its main difference with every other Bitcoin client/wallet out there is its low resource requirements: the binary is currently 25 kilobytes large, it uses less than 2 kilobytes of RAM and requires only 160 bytes of non-volatile storage per wallet. With such low requirements, I reckon a production device would be smaller, more robust and cheaper than any other Bitcoin wallet.

The wallet stores private keys (actually, it only stores a seed for the deterministic key generator), parses transactions and signs transactions. It essentially doesn't do anything else. This is by design - simpler means a smaller attack surface. Private keys are generated on the device and never leave the device, except when doing a wallet backup. Even then, the seed is only displayed - it is never sent over the serial port. My intention is that physical access to a device is required in order to obtain private keys or to spend anything. As an additional layer of security, wallets can be encrypted. An encrypted wallet offers pseudo-two-factor authentication: in order to spend BTC, you need to  *know*  the wallet passphrase and you need to  *have*  the hardware Bitcoin wallet.