Despite the security community's best effort, the number of serious vulnerabilities discovered in software is increasing rapidly. In theory, security audits should find and remove the vulnerabilities before the code ever gets deployed. However, due to the enormous amount of code being produced, as well as a the lack of manpower and expertise, not all code is sufficiently audited. Thus, many vulnerabilities slip into production systems. A best-practice approach is to use a code metric analysis tool, such as Flawfinder, to flag potentially dangerous code so that it can receive special attention. However, because these tools have a very high false-positive rate, the manual effort needed to find vulnerabilities remains overwhelming. In this paper, we present a new method of finding potentially dangerous code in code repositories with a significantly lower false-positive rate than comparable systems. We combine code-metric analysis with metadata gathered from code repositories to help code review teams prioritize their work. The paper makes three contributions. First, we conducted the first large-scale mapping of CVEs to GitHub commits in order to create a vulnerable commit database. Second, based on this database, we trained a SVM classifier to flag suspicious commits. Compared to Flawfinder, our approach reduces the amount of false alarms by over 99 % at the same level of recall. Finally, we present a thorough quantitative and qualitative analysis of our approach and discuss lessons learned from the results. We will share the database as a benchmark for future research and will also provide our analysis tool as a web service.

Motivated by recent revelations of widespread state surveillance of personal communication, many solutions now claim to offer secure and private messaging. This includes both a large number of new projects and many widely adopted tools that have added security features. The intense pressure in the past two years to deliver solutions quickly has resulted in varying threat models, incomplete objectives, dubious security claims, and a lack of broad perspective on the existing cryptographic literature on secure communication. In this paper, we evaluate and systematize current secure messaging solutions and propose an evaluation framework for their security, usability, and ease-of-adoption properties. We consider solutions from academia, but also identify innovative and promising approaches used "in-the-wild" that are not considered by the academic literature. We identify three key challenges and map the design landscape for each: trust establishment, conversation security, and transport privacy. Trust establishment approaches offering strong security and privacy features perform poorly from a usability and adoption perspective, whereas some hybrid approaches that have not been well studied in the academic literature might provide better trade-offs in practice. In contrast, once trust is established, conversation security can be achieved without any user involvement in most two-party conversations, though conversations between larger groups still lack a good solution. Finally, transport privacy appears to be the most difficult problem to solve without paying significant performance penalties.

Previous research showed that the SSL infrastructure is a fragile system: X.509 certificate validation fails for a non-trivial number of HTTPS-enabled websites resulting in SSL warning messages presented to users. Studies revealed that warning messages do not provide easy-to-understand information or are ignored by webbrowser users. SSL warning messages are a critical component in the HTTPS infrastructure and many attempts have been made to improve these warning messages. However, an important question has not received sufficient attention yet: Why do webmasters (deliberately) deploy non-validating, security-critical X.509 certificates on publicly available websites? In this paper, we conduct the first study with webmasters operating non-validating X.509 certificates to understand their motives behind deploying those certificates. We extracted the non-validating certificates from Google's webcrawler body of X.509 certificates, informed webmasters about the problem with the X.509 certificate configuration on their website and invited a random sample of the respective webmasters to participate in our study. 755 webmasters participated, allowing us insight into their motives. While one third of them admitted to having misconfigured their webserver accidentally, two thirds of them gave reasons for deliberately using a non-validating X.509 certificate.

Mobile devices are evolving as the dominant computing platform and consequently application repositories and app markets are becoming the prevalent paradigm for deploying software. Due to their central and trusted position in the software ecosystem, coerced, hacked or malicious app markets pose a serious threat to user security. Currently, there is little that hinders a nation state adversary (NSA) or other powerful attackers from using such central and trusted points of software distribution to deploy customized (malicious) versions of apps to specific users. Due to intransparencies in the current app installation paradigm, this kind of attack is extremely hard to detect.

The Secure Sockets Layer (SSL) is widely used to secure data transfers on the Internet. Previous studies have shown that the state of non-browser SSL code is catastrophic across a large variety of desktop applications and libraries as well as a large selection of Android apps, leaving users vulnerable to Man-in-the-Middle attacks (MITMAs). To determine possible causes of SSL problems on all major appified platforms, we extended the analysis to the walled-garden ecosystem of iOS, analyzed software developer forums and conducted interviews with developers of vulnerable apps. Our results show that the root causes are not simply careless developers, but also limitations and issues of the current SSL development paradigm. Based on our findings, we derive a proposal to rethink the handling of SSL in the appified world and present a set of countermeasures to improve the handling of SSL using Android as a blueprint for other platforms. Our countermeasures prevent developers from willfully or accidentally breaking SSL certificate validation, offer support for extended features such as SSL Pinning and different SSL validation infrastructures, and protect users. We evaluated our solution against 13,500 popular Android apps and conducted developer interviews to judge the acceptance of our approach and found that our solution works well for all investigated apps and developers.

Data protection is a challenge when outsourcing medical analysis, especially if one is dealing with patient related data. While securing transfer channels is possible using encryption mechanisms, protecting the data during analyses is difficult as it usually involves processing steps on the plain data. A common use case in bioinformatics is when a scientist searches for a biological sequence of amino acids or DNA nucleotides in a library or database of sequences to identify similarities. Most such search algorithms are optimized for speed with less or no consideration for data protection. Fast algorithms are especially necessary because of the immense search space represented for instance by the genome or proteome of complex organisms. We propose a new secure exact term search algorithm based on Bloom filters. Our algorithm retains data privacy by using Obfuscated Bloom filters while maintaining the performance needed for real-life applications. The results can then be further aggregated using Homomorphic Cryptography to allow exact-match searching. The proposed system facilitates outsourcing exact term search of sensitive data to on-demand resources in a way which conforms to best practice of data protection.

Homomorphic cryptography has received a lot of attention due to potentially ground breaking advances in cryptography. However it is also surrounded by a lot of hyperbole such as "ground breaking advances", "this will solve all Cloud computing problems" to "it is completely impractical" and "it will never work for real world problems". In previous work we showed how homomorphic encryption can be used to execute arbitrary programs in encrypted space, showing that at least in theory real world problems can be computed protected by homomorphic cryptography without losing generality. In this paper we expand our work to evaluate how practical current homomorphic cryptography based on the Smart-Vercauteren system is for executing arbitrary programs on untrusted resources. For this we present the implementation of a method to compute non-linear secret programs on an untrusted resource using encrypted circuits embedded in an encrypted virtual machine. We successively show how a processor architecture using encrypted circuits can be implemented so it can support read and write memory access, dynamic parameters and non-linear programs that render branch-decisions at runtime. The system comprises the runtime environment for program execution and an assembler to generate the encrypted machine code. We present performance evaluation of the sub-components as well as the complete system. The system represents a flexible prototype for homomorphic program execution in software and system architecture.