{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,6,18]],"date-time":"2025-06-18T04:27:46Z","timestamp":1750220866348,"version":"3.41.0"},"reference-count":31,"publisher":"Association for Computing Machinery (ACM)","issue":"1","license":[{"start":{"date-parts":[[2020,9,28]],"date-time":"2020-09-28T00:00:00Z","timestamp":1601251200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/www.acm.org\/publications\/policies\/copyright_policy#Background"}],"funder":[{"name":"COMMANDO-HUMANS project","award":["EP\/N020111\/1"],"award-info":[{"award-number":["EP\/N020111\/1"]}]}],"content-domain":{"domain":["dl.acm.org"],"crossmark-restriction":true},"short-container-title":["ACM Trans. Priv. Secur."],"published-print":{"date-parts":[[2021,2,28]]},"abstract":"<jats:p>Observation Resilient Authentication Schemes (ORAS) are a class of shared secret challenge\u2013response identification schemes where a user mentally computes the response via a cognitive function to authenticate herself such that eavesdroppers cannot readily extract the secret. Security evaluation of ORAS generally involves quantifying information leaked via observed challenge\u2013response pairs. However, little work has evaluated information leaked via human behavior while interacting with these schemes. A common way to achieve observation resilience is by including a modulus operation in the cognitive function. This minimizes the information leaked about the secret due to the many-to-one map from the set of possible secrets to a given response. In this work, we show that user behavior can be used as a side channel to obtain the secret in such ORAS. Specifically, the user\u2019s eye-movement patterns and associated timing information can deduce whether a modulus operation was performed (a fundamental design element) to leak information about the secret. We further show that the secret can still be retrieved if the deduction is erroneous, a more likely case in practice. We treat the vulnerability analytically and propose a generic attack algorithm that iteratively obtains the secret despite the \u201cfaulty\u201d modulus information. We demonstrate the attack on five ORAS and show that the secret can be retrieved with considerably less challenge\u2013response pairs than non-side-channel attacks (e.g., algebraic\/statistical attacks). In particular, our attack is applicable on Mod10, a one-time-pad-based scheme, for which no non-side-channel attack exists. We field test our attack with a small-scale eye-tracking user study.<\/jats:p>","DOI":"10.1145\/3414844","type":"journal-article","created":{"date-parts":[[2020,9,28]],"date-time":"2020-09-28T11:02:35Z","timestamp":1601290955000},"page":"1-33","update-policy":"https:\/\/doi.org\/10.1145\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Exploiting Behavioral Side Channels in Observation Resilient Cognitive Authentication Schemes"],"prefix":"10.1145","volume":"24","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-2774-2675","authenticated-orcid":false,"given":"Benjamin Zi Hao","family":"Zhao","sequence":"first","affiliation":[{"name":"University of New South Wales and Data61, CSIRO, Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hassan Jameel","family":"Asghar","sequence":"additional","affiliation":[{"name":"Macquarie University and Data61, CSIRO, Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mohamed Ali","family":"Kaafar","sequence":"additional","affiliation":[{"name":"Macquarie University and Data61, CSIRO, Australia"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Francesca","family":"Trevisan","sequence":"additional","affiliation":[{"name":"University of Surrey, United Kingdom"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Haiyue","family":"Yuan","sequence":"additional","affiliation":[{"name":"University of Surrey, United Kingdom"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"320","published-online":{"date-parts":[[2020,9,28]]},"reference":[{"volume-title":"Proceedings of the 20th Annual Network and Distributed System Security Symposium. 1--18","year":"2013","author":"Asghar Hassan Jameel","key":"e_1_2_1_1_1"},{"key":"e_1_2_1_2_1","doi-asserted-by":"publisher","DOI":"10.1007\/978-3-642-13708-2_21"},{"key":"e_1_2_1_3_1","doi-asserted-by":"publisher","DOI":"10.1109\/TIFS.2015.2421875"},{"volume-title":"Proceedings of the 4th USENIX Conference on Offensive Technologies. 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