A Bitcoin Wallet for the Masses: Square simplified credit-card transactions. Now it wants to build cryptocurrency hardware

A Wallet to hold bitcoins―or other cryptocurrencies―is not at all a new idea. Basically a souped-up flash drive, these gadgets hold a private key, protected by a pin or passcode, that allows a user to securely access cryptocurrency data; the data itself lives in the blockchain. Some of these “wallets” have their own displays, some require use with a computer or phone.