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Passwords are still a mainstay of various security systems, as well as the cause of many usability issues. For end-users, many of these issues have been studied extensively, highlighting problems and informing design decisions for better policies and motivating research into alternatives. However, end-users are not the only ones who have usability problems with passwords! Developers who are tasked with writing the code by which passwords are stored must do so securely. Yet history has shown that this complex task often fails due to human error with catastrophic results. While an end-user who selects a bad password can have dire consequences, the consequences of a developer who forgets to hash and salt a password database can lead to far larger problems. In this paper we present a first qualitative usability study with 20 computer science students to discover how developers deal with password storage and to inform research into aiding developers in the creation of secure password systems. * These authors contributed equally to this work.

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With WhatsApp's adoption of the Signal Protocol as its default, end-to-end encryption by the masses happened almost overnight. Unlike iMessage, WhatsApp notifies users that encryption is enabled, explicitly informing users about improved privacy. This rare feature gives us an opportunity to study people's understandings and perceptions of secure messaging pre-and post-mass messenger encryption (pre/post-MME). To study changes in perceptions, we compared the results of two mental models studies: one conducted in 2015 pre-MME and one in 2017 post-MME. Our primary finding is that users do not trust encryption as currently offered. When asked about encryption in the study, most stated that they had heard of encryption, but only a few understood the implications, even on a high level. Their consensus view was that no technical solution to stop skilled attackers from getting their data exists. Even with a major development, such as WhatsApp rolling out endto-end encryption, people still do not feel well protected by their technology. Surprisingly, despite WhatsApp's end-to-end security info messages and the high media attention, the majority of the participants were not even aware of encryption. Most participants had an almost correct threat model, but don't believe that there is a technical solution to stop knowledgeable attackers to read their messages. Using technology made them feel vulnerable.

Abstract. The sheer size of commodity operating system kernels makes them a prime target for local attackers aiming to escalate privileges. At the same time, as much as 90% of kernel functions are not required for processing system calls originating from a typical network daemon. This results in an unnecessarily high exposure. In this paper, we introduce kRazor, an approach to reduce the kernel's attack surface by limiting the amount of kernel code accessible to an application. KRAZOR first traces individual kernel functions used by an application. KRAZOR can then detect and prevent uses of unnecessary kernel functions by a process. This step is implemented as a kernel module that instruments select kernel functions. A heuristic on the kernel function selection allows KRAZOR to have negligible performance overhead. We evaluate results under real-world workloads for four typical server applications. Results show that the performance overhead and false positives remain low, while the attack surface reduction can be as high as 80%.