Analysis and Improvement on a Unimodal Haptic PIN-Entry Method

Table 3

Comparison of usability and security of various PIN-entry methods (TCT (task completion time): PIN-entry time, Error rate: rate of erroneous input in three trials, Comp.: compatibility with legacy 4-digit PIN, : success probability of attacker’s log-on (in three trials) by randomly guessing a PIN, and : success probability of attacker’s log-on (in three trials) after observing one PIN-entry session).

Method	TCT (s)	Error rate	Comp.
Regular		NA	◯	0.0003	≈1.0
Undercover [12]	32–45	>0.315		0.00015	≪0.0001
Vibrapass [14]	3.9–8.2	>0.148	◯	0.0003	0.04–0.6
Haptic Wheel [15]	23.0–23.5	0.16–0.18		<0.0002	<0.0002
Spinlock [19]	13.9–20.1	0.07–0.08		≤0.0003	NA
Colorlock [19]	10.0–10.1	0.05–0.09		0.0002
Timelock [19]	8.0–10.8	0.02–0.04		0.0002	0.0768
TictocPIN [28]	15.8	0.0	◯	0.0003	0.0048
Addlock	18.0	0.0056	◯	0.0003	0.0003
Map lock	20.6	0.0056	◯	0.0003	0.0003
Counter Phone Lock	27.6	0.0056	◯	0.0003	0.0003

from [8], is the claimed value in [12], which is significantly smaller in practice. in parentheses represent reset rates (rates of canceled trials). value assuming that the randomization parameters for Colorlock and Timelock are the same.