Bio-Pen's built-in sensors have been expressly created for it; thus, it is difficult to foresee their output simply observing them from the outside.

Rough information originating from the sensors are codified by the Micro Computer Unit within the pen, so that the pen's output is protected.

Movements of the pen's body (internal data) can be compared to the movement of its writing end (used as a mouse or a stylus) and effectively employed to verify whether the individual repeats the same writing movement.

The MCU's firmware within the pen's body has been expressly designed to pre-process all the data and to communicate with the host PC. The firmware cannot be overwritten by anyone, as the initial programming PIN is destroyed at the plant before the whole Bio-Pen's circuit is plunged into epoxy resin and covered by the pen's body.

The first feature consists in a single unique ID that characterizes each pen, which is employed by the codification algorithm. The second feature is that each pen can generate data in real time by receiving a unique code by the host software; this implies that the MCU generates different data each time a subject signs with Bio-Pen and that signature data are valid for a single use.