GreenAddress Bitcoin mobile wallet is now renamed Blockstream Green. This app is already available for download on Android and iOS devices, and more platforms will be launched soon. Codes for these two apps It is also open source and can be found on GitHub. Like the previous GreenAddress, Green Wallet uses 2-of-2 multi-signature by default. One key is stored on the device and one key is stored on the Blockstream server. This can be achieved Application-based two-factor authentication (2FA), so that if the user’s device is lost or stolen, the attacker cannot use his funds (it is recommended that the user hold his 2FA on a separate device).