The standard way to unlock a device is with a password. TPMs have improved this to the point that we can create devices that can be unlocked with very short passwords such as PINs and we can create devices that are resistant even in the face of physical access to the device.
However, almost all devices have the flaw that if an adversary observes you unlocking the device one time, the device is completely compromised. For this reason, Edward Snowden goes under a blanket every time he enters his password.
Is there an alternative that is more convenient? It doesn't necessarily have to be resistant to cryptanalysis of many observed password entries, but it should resist at least a layperson viewing password entries several times.
If it helps, we could assume that every several logins there is one that is unobserved.
