Thesis - Instituto de Telecomunicações

6.2. SYMPATHETIC DYNAMICS BIOMETRICS 121Guessing Entropy (bits)252015105Level 2Level 1PIN code + mouse interactionUser selected PIN codeMouse movement clicking n digitis00 5 10 15Lenght of PIN codeFigure 6.3: Guessing Entropy of: (i) mouse movement biometric; (ii) PIN code; (iii) combinationof mouse movement biometric and PIN code.6.2 Sympathetic Dynamics BiometricsFrom the three studied signals, the electrodermal activity data is the one with the poorestdata separability among users. This presents a complex problem in deciding if this data isuseful and what techniques to use with the EDA signal. In this case, we use the extensionproposed for classification fusion in cases of highly overlapping data among the classes. Wedescribe the data, the base results in a stand alone mode and the results when fusing thisbiometric trait with a classifier based on well separated synthetic data.6.2.1 Data PreparationAn EDA event, called a skin conductance response, is a detected response in the Electrodermalsignal as described in section 4.2. The electrodermal activity was recorded simultaneouslywith the ECG, in the execution of a concentration test. For performance evaluationwe selected a random set of events from each user guaranteeing that the set dimension isequal to every user. We used 125 samples per each of the 27 users. The person was performingthe concentration test, where the user had to select pairs of numbers that add to