1. A computer based system for acquisition, analysis and authentication of the handwritten signature comprising a pen-subsystem for acquiring signals and transmitting information to further subsystems integrated in a personal computer which, in its turn, is network connected to further subsystems integrated in server, which, in its turn, may or may not be network connected to other personal computers each having connected as peripheral a pen-subsystem, wherein, the pen-subsystem comprises: a metallic case for electromagnetic shielding; two MEMS acceleration sensor groups, placed in two different parallel planes with the same orientation regarding their x, y orthogonal sensing axes, and having set the frequency band response between 0 Hz and 100 Hz for capturing two acceleration signals from each the sensor group, all four signals containing the manifestation of two simultaneous phenomena, the first phenomenon being the contact micro vibrations generated by the feedback loop type interaction of the hand-guided pen movements with the paper during writing, manifesting in a frequency range of between 10 to 60 Hz and, the second phenomenon being the tri-dimensional spatial hand and pen movements during writing, namely spatial kinetic information, manifesting in a frequency range of between 0 to 10 Hz; a pen refill with a writing lead and a body made of plastic material that allows the transmission of the frequency band specific to the contact micro vibrations; a printed circuit board, having a thickness lower than 0.5 mm, in permanent contact with the pen refill body, on the printed circuit board both the sensor groups being placed under a fixed angle equal to 45°, between the writing tip of the pen and the sensor group being a distance lower than 15 mm, and between the two sensor groups being a distance higher than 30 mm, the distance being necessary to capture the contact micro vibrations transmitted from the pen refill through the printed circuit board to sensor groups, and the distance being necessary to capture the spatial kinetic information; an infrared LED and infrared light sensor, both placed in the writing top of the pen-subsystem, sensor taking over a quantity of infrared light emitted by infrared LED and reflected from the paper; a microcontroller for acquisition, digitizing and coding of the signals from the sensor groups and from sensor, at a sampling rate of 1000 Hz, the signal from sensor being compared to a predetermined threshold value in order to generate the context information as a boolean value which is 1 if, and only if, the pen-subsystem is in proximity of the paper, and in a proper writing position, the resulting digitized signals, namely ax, ay from sensor group, bx, by from sensor group and the context information from sensor, being coded together and serialized; a micro system for the conversion and transmission of the serial data from the microcontroller in USB format; and a USB connection cable for the transmission of the data from the micro system to the subsystem, the cable having a no more than 2.5 mm diameter, so that to have a minimal influence on the hand gestures during writing.