Quote from: vite on May 24, 2018, 08:40:57 AM

And also there is pi wallet which is similar to that of a small computer which is not mentioned by any other user. Transaction are signed offline in Pi wallet and transfeered to usb

One should note that transferring transactions via USB can impose a new risk of getting infected.
While this is a (relatively) uncommon attack vector, it still does exist.

Since you are using an USB storage to 'communicate' between your offline storage and your online PC, it effectively isn't fully air-gapped anymore.

An approach to negate that attack vector would be to use QR codes and webcams (on your PI and online PC) to transmit data (un-/signed transactions).