Let's Read: Analysing S/MIME Certificate Vendors' Efficiency and Privacy

Email is one of the oldest and most popular applications on today's Internet and is used for business and private communication. However, most emails are still susceptible to being intercepted or even manipulated by the servers transmitting the messages. Users with S/MIME certificates can protect their email messages. In this paper, we investigate the market for S/MIME certificates and analyse the impact of the ordering and revocation processes on the users' privacy. We complete those processes for each vendor and investigate the number of requests, the size of the data transfer, and the number of trackers on the vendor's Web site. We further collect all relevant documents, including privacy policies, and report on their number of words, readability, and quality. Our results show that users must make at least 86 HTTP requests and transfer at least 1.35 MB to obtain a certificate and 178 requests and 2.03 MB to revoke a certificate. All but one vendor employ third-party tracking during these processes, which causes between 43 and 354 third-party requests. Our results further show that the vendors' privacy policies are at least 1701 words long which requires a user approximately 7 minutes to read. The longest policy requires approximately half an hour to be read. Measurements of the readability of all vendors' privacy policies indicate that users need a level of education that is nearly equivalent to a bachelor's degree to comprehend the texts. We also report on the quality of the policies and find that the vendors achieve compliance scores between 45 % and 90 %. With our method, vendors can measure their impact on the users' privacy and create better products. On the other hand, users benefit from an analysis of all S/MIME certificate vendors in that they can make an informed choice of their vendor based on the objective metrics obtained by our study. Ultimately, the results help to increase the prevalence of encrypted emails and render society less susceptible to surveillance.