Armory is the most solid and secure Bitcoin wallet. Bitcoin wallet technology is complex and Armory is the most secure and feature-rich Bitcoin wallet application. Armory pioneered the "cold storage" concept of storing and transacting Bitcoin funds where the private keys are stored only on a computer that is kept entirely offline and supports backing up Bitcoin funds to a printed paper backup. Armory is tailored for standard, advanced and expert Bitcoin users and is licensed under the "AGPL version 3" which guarantees that Armory and any derivative programs based on Armory source-code will always be open-source.