What is the most secure lock method?

[plasticman99]

Password may be remembered by others. Face detection may be unlocked by the one with similar face. What is the most secure way to lock the phone?

 

[Rukbat]

A 20 character random mixed alpha upper and lower/numeric/punctuation password is called "military strength". VERY few people on the planet can remember even one of them (And by very few, I mean they could all fit into the average size bedroom comfortably at one time - out of more than 7 billion people.) Fingerprint scanning is also pretty secure. (Wait a few years and we'll have retinal scanning in phones.)

 

[plasticman99]

20 character password may be secure, but maybe a bit inconvenient...