Is the hidden blade mechanism in assassins creed possible and if so how does it work?

The hidden blade as shown within the game is a fantasy weapon. While it may be backed by some mechanical work, designing one with the identical use and look may be impossible.

Official concept art of Altair's hidden blade show a mechanism similar to a scissor lift, activated by the tug of pinky ring.

Ezio's blade is a different style and most likely operates on a system of springs and locks.