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Instead of ignoring it, we should decrease his importance. Fig. 5. Features weights study Finally, the transient study was repeated but this time taking into account the previous best configurations (the best acceptance neighbourhood parameters and the best weights previously presented). Fig. 6 shows S(AS(l)) for different values of l. As we can see, the value stays stable during all the reduction process (starting with l = 750). After 20 reductions, the value shows no relevant fluctuations. This means a reduction of 80%, equivalent to a reduction of around 600 keys.

The classical example for transients is the harmonic oscillator[11]. In our mechanism, we have S(AS(l))l→∞ −→ a with a representing the characteristic value for the user (in theory close to 1). Here, the transients are the values we get when l is too small and, consequently, are not user representative. Identifying the minimum l for which we do not have any more transients means identifying the minimum size of the sample to get a reasonable value for a. Fig. 3 shows the transients study using 3 samples with 750 keys each from 3 different users.

We can thus send AT commands to make phone calls or send SMS to premium cost numbers. This way making the attacker earn money, or more accurately stealing it. Complementing this, some manufacturers extend this list, adding some proprietary commands, with the purpose of enabling control and capabilities that they want to have on the system. These commands are private and manufacturers do not publish them. But without the use of some form of encryption, anyone is able to eavesdrop the communication channel and try to understand, what lies under the system.