| | Locking system | Description |
| | Pattern lock | This authentication system uses end user’s visual memory. Using nine points in a three-by-three grid, a user creates a drag pattern. This method belongs not only to the something you know category, which is based on memory, but also to the behavior pattern recognition category, since it utilizes finger motion memory. The number of available secret patterns in this system is 388,912, which is relatively small due to the limited and fixed arrangement of the nine possible points. This method can be vulnerable to a brute force attack if a user creates a drag pattern using a fewer than suggested number of points to unlock the screen faster. It is also vulnerable to a shoulder surfing attack by malicious attackers due to the visual aspects of a drag pattern. Finally, it is vulnerable to the smudge attack as well, which uses the characteristics of touch screen, in case of theft. |
| | Face recognition | This authentication mode uses biometric information. This method depends on the camera in smart devices and has the advantage of requiring additional memory or management of the locking key due to unique characteristics. However, unlocking the locked screen could be difficult not only due to low performance of the embedded camera but also due to environmental factors (e.g., face recognition range can be limited because of the amount of ambient light). Further, it is vulnerable to the application of similar faces or recognition using photos and videos, which is why this method, in general, is rarely used. |
| | Password | This authentication system uses visual memory and is familiar to most users. Passwords are used by offering a virtual keypad where a combination of alphabetic, numeric, and special characters can be used. Security is dependent on the strength of the password, which depends on the combination of chosen characters. If a password is considerably short in length, for quicker screen unlocking, then it could be vulnerable to a smudge or shoulder surfing attack. If the length of password is considerably long, the user may experience password memory loss possibly due to confusion. Password is also vulnerable to the dictionary attack if the attacker has access to the user’s personal information. |
| | PIN | This authentication system has yet to overcome confusion due to the complicated combination of characters used for a password. PIN uses only a numerical value from 0 to 9. Further, it uses combinations of only four numbers so that the available PIN count is less than 10,000, which is considerably small. Thus, it is vulnerable to a brute force attack. It is also vulnerable to shoulder surfing and smudge attacks due to generated traces and the visual nature of pressing four numbers. |
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