Parity Technologies continues to test a mobile app for cold storage of keys to cryptocurrency wallets compatible with Polkadot and Ethereum.
Parity Signer (https://www.parity.io/signer/) is designed for offline use. The mobile device used to run the application will contain important information that needs to be stored securely. Actually with its help it is possible to turn any mobile device into a hardware wallet.
Please take into account (security advice):
Use a special dedicated mobile device for Signer (not your regular phone)
Make a return to the factory settings
Wi-Fi, mobile network, Bluetooth should be disconnected
Enable full disk encryption on a device with a reasonable password
Do not use any biometric data such as fingerprints or facial recognition to decrypt/unlock the device, as it may be less secure than a normal password
After installing the application, turn on the flight mode and be sure to turn off Wi-Fi, Bluetooth or any device connection possibility
Charge your phone only from a socket that is never connected to the Internet
Charge your phone only using the manufacturer's charging adapter
Do not charge your phone from public USB chargers
