Signature recognition is a behavioural biometric. It can be operated in two different ways:
Static: In this mode, users write their signature on paper, digitize it through an optical scanner or a camera, and the biometric system recognizes the signature analyzing its shape. This group is also known as "off-line".
Dynamic: In this mode, users write their signature in a digitizing tablet, which acquires the signature in real time. Another possibility is the acquisition by means of stylus-operated PDAs. Some systems also operate on smart-phones or tablets with a capacitive screen, where users can sign using a finger or an appropriate pen. Dynamic recognition is also known as "on-line". Dynamic information usually consists of the following information:
- spatial coordinate x(t)
- spatial coordinate y(t)
- pressure p(t)
- azimuth az(t)
- inclination in(t)
- pen up/down
The state-of-the-art in signature recognition can be found in the last major international competition.
The most popular pattern recognition techniques applied for signature recognition are dynamic time warping, hidden Markov models and vector quantization. Combinations of different techniques also exist.
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