Investigating the effects of sound masking on the use of audio CAPTCHAs

Abstract

The SoundsRight Audio Completely Automated Public Turing tests to tell Computers and Humans Apart (CAPTCHA) was developed with the goal of providing a usable and secure audio CAPTCHA for people with visual impairments. Its design requires users to repeatedly identify a specific sound from a group of different sounds (e.g. baby crying and bird chirping) in real time. Adding background noise (sound masks) to the sounds may make it more difficult for automated software to recognise the sounds and therefore, improve security. However, the sound masks may also make it more challenging for human users to recognise the sound. We conducted a user study involving 20 blind participants and 20 sighted participants to investigate the effect of sound masks on the usability of the SoundsRight CAPTCHA. The results suggest that sound masks do have a significant impact on the failure rate and response time. Sighted participants had significantly a higher failure rate than blind participants and were more vulnerable to the negative effect of sound masks.

Usable Security: A Systematic Literature Review

“…However, the choice of HIPs should be carefully made depending on the users' attributes, who can perceive HIPs in different ways. Olalere et al, 2014 show that visually impaired users have a higher success rate in solving audio-based CAPTCHAs compared to normal-sighted users. In contrast, text-based CAPTCHAs are demonstrated to be more difficult for foreigners [21].…”

“…The sub-clusters were as follows: Completely Automated Public Turing test to tell Computers and Humans Apart (CAPTCHA): One of the tools investigated is CAPTCHA tests [14,[16][17][18][19][20]. CAPTCHA is a security measure known as Challenge/Response authentication, aimed at protecting users from spam and password decryption by asking them to pass a simple test that proves the user is a person and not a computer attempting to hack a password-protected account.…”

“…Nevertheless, alternative tools to common text passwords are difficult to use in some contexts and are characterized by vulnerabilities due to the human factor. The predictability of patterns [4] was analyzed, often replacing textual elements with graphical ones [4,15,[23][24][25] and sound-based ones [20].…”

“…Usability evaluation of existing and novel systems: Contributions belonging to this category seem to be characterized by two main approaches to evaluating the products/methods: authors either evaluate them individually [20,25,27,29,[34][35][36][37] or compare them with other existing or new systems [4,[13][14][15][16][17][18][19]22,24,26,28,30,32,33,[38][39][40][41].…”

A Novel Design of Audio CAPTCHA for Visually Impaired Users

“…The evaluation study with 20 blind users indicates that the SoundsRight CAPTCHA is easy to use, and the success rate is reported as 95%. To make it more secure, Olalere et al improved the SoundsRight CAPTCHA by adding background noise and the user study shows that blind users could solve the CAPTCHA challenges better than sighted users [30]. Another interesting CAPTCHA method uses multimodal challenge tasks by using images with corresponding audio clips to permit easy access for both blind and sighted people [31].…”