SiteKey uses the following challenge–response technique:345
If the user is at a phishing site with a different Web site domain than the legitimate domain, the user's browser will refuse to send the state token in step (2); the phishing site owner will either need to skip displaying the correct security image, or prompt the user for the security question(s) obtained from the legitimate domain and pass on the answers. In theory, this could cause the user to become suspicious, since the user might be surprised to be re-prompted for security questions even if they have used the legitimate domain from their browser recently. However, in practice, there are evidence users generally fail to notice such anomalies.6
A Harvard study78 found SiteKey 97% ineffective. In practice, real people don't notice, or don't care, when the SiteKey is missing, according to their results.
It also requires users to keep track of more authentication information. Someone associated with N different websites that use SiteKey must remember N different 4-tuples of information: (site, username, phrase, password).
In May 2015, Bank of America announced that SiteKey would be discontinued for all users by the end of the year, and would allow users to log in with their username and password in one step.9 In July 2015, Vanguard also discontinued the use of SiteKey for its website.10
"More security tools and simpler sign-in at Bank of America". Archived from the original on 2015-05-10. Retrieved 2015-05-10. https://web.archive.org/web/20150510024701/http://info.bankofamerica.com/new-sign-in/ ↩
"We've streamlined the process for logging on to Vanguard.com". Archived from the original on 2016-03-04. https://web.archive.org/web/20160304054144/https://personal.vanguard.com/us/insights/article/Single-Signon-072015 ↩
"Bank of America Online and Mobile Banking FAQs". https://www.bankofamerica.com/privacy/faq/sitekey-faq.go ↩
Jim Youll (18 July 2006). "Fraud Vulnerabilities in SiteKey Security at Bank of America" (PDF). Archived from the original (PDF) on 2016-12-31. https://web.archive.org/web/20161231004055/http://cr-labs.com/publications/SiteKey-20060718.pdf ↩
Stuart E. Schechter; Rachna Dhamija; Andy Ozment; Ian Fischer (4 February 2007). "The Emperor's New Security Indicators" (PDF). http://www.usablesecurity.org/emperor/emperor.pdf ↩
Joel Hruska (20 June 2007). "Security study pokes holes in advanced authentication claims". Ars Technica. https://arstechnica.com/security/2007/06/sec/ ↩
Schecter; Dhamija; Ozment; Fischer (2007-05-20). "The Emperor's New Security Indicators: An evaluation of website authentication and the effect of roleplaying on usability studies" (PDF). Archived from the original (PDF) on 2007-09-27. Retrieved 2020-04-23. {{cite journal}}: Cite journal requires |journal= (help) https://web.archive.org/web/20070927171729/http://people.seas.harvard.edu/~rachna/papers/emperor-security-indicators-bank-sitekey-phishing-study.pdf ↩