Passphone: Outsourcing Phone-based Web Authentication while Protecting User Privacy

This work introduces PassPhone, a new smartphone-based authentication scheme that outsources user verification to a trusted third party without sacrificing privacy: neither can the trusted third party learn the relation between users and service providers, nor can service providers learn those of their users to others. When employed as a second factor in conjunction with, for instance, passwords as a first factor, our scheme maximizes the deployability of two-factor authentication for service providers while maintaining user privacy. We conduct a twofold formal analysis of our scheme, the first regarding its general security, and the second regarding anonymity and unlinkability of its users. Moreover, we provide an automatic analysis using AVISPA, a comparative evaluation to existing schemes under Bonneau et al.\u27s framework, and an evaluation of a prototypical implementation

Mitigating Botnet-based DDoS Attacks against Web Servers

Distributed denial-of-service (DDoS) attacks have become wide-spread on the Internet. They continuously target retail merchants, financial companies and government institutions, disrupting the availability of their online resources and causing millions of dollars of financial losses. Software vulnerabilities and proliferation of malware have helped create a class of application-level DDoS attacks using networks of compromised hosts (botnets). In a botnet-based DDoS attack, an attacker orders large numbers of bots to send seemingly regular HTTP and HTTPS requests to a web server, so as to deplete the server's CPU, disk, or memory capacity. Researchers have proposed client authentication mechanisms, such as CAPTCHA puzzles, to distinguish bot traffic from legitimate client activity and discard bot-originated packets. However, CAPTCHA authentication is vulnerable to denial-of-service and artificial intelligence attacks. This dissertation proposes that clients instead use hardware tokens to authenticate in a federated authentication environment. The federated authentication solution must resist both man-in-the-middle and denial-of-service attacks. The proposed system architecture uses the Kerberos protocol to satisfy both requirements. This work proposes novel extensions to Kerberos to make it more suitable for generic web authentication. A server could verify client credentials and blacklist repeated offenders. Traffic from blacklisted clients, however, still traverses the server's network stack and consumes server resources. This work proposes Sentinel, a dedicated front-end network device that intercepts server-bound traffic, verifies authentication credentials and filters blacklisted traffic before it reaches the server. Using a front-end device also allows transparently deploying hardware acceleration using network co-processors. Network co-processors can discard blacklisted traffic at the hardware level before it wastes front-end host resources. We implement the proposed system architecture by integrating existing software applications and libraries. We validate the system implementation by evaluating its performance under DDoS attacks consisting of floods of HTTP and HTTPS requests

A scalable and dynamic application-level secure communication framework for inter-cloud services

Most of the current cloud computing platforms offer Infrastructure as a Service (IaaS) model, which aims to provision basic virtualized computing resources as on-demand and dynamic services. Nevertheless, a single cloud does not have limitless resources to offer to its users, hence the notion of an Inter-Cloud environment where a cloud can use the infrastructure resources of other clouds. However, there is no common framework in existence that allows the service owners to seamlessly provision even some basic services across multiple cloud service providers, albeit not due to any inherent incompatibility or proprietary nature of the foundation technologies on which these cloud platforms is built. In this paper we present a novel solution which aims to cover a gap in a subsection of this problem domain. Our solution offers a security architecture that enables service owners to provision a dynamic and service-oriented secure virtual private network on top of multiple cloud IaaS providers. It does this by leveraging the scalability, robustness and exibility of peer-to-peer overlay techniques to eliminate the manual configuration, key management and peer churn problems encountered in setting up the secure communication channels dynamically, between different components of a typical service that is deployed on multiple clouds. We present the implementation details of our solution as well as experimental results carried out on two commercial clouds

Understanding the trust relationships of the web PKI

TLS and the applications it secures (e.g., email, online banking, social media) rely on the web PKI to provide authentication. Without strong authentication guarantees, a capable attacker can impersonate trusted network entities and undermine both data integrity and confidentiality. At its core, the web PKI succeeds as a global authentication system because of the scalability afforded by trust. Instead of requiring every network entity to directly authenticate every other network entity, network entities trust certification authorities (CAs) to perform authentication on their behalf. Prior work has extensively studied the TLS protocol and CA authentication of network entities (i.e., certificate issuance), but few have examined even the most foundational aspect of trust management and understood which CAs are trusted by which TLS user agents, and why. One major reason for this disparity is the opacity of trust management in two regards: difficult data access and poor specifications. It is relatively easy to acquire and test popular TLS client/server software and issued certificates. On the other hand, tracking trust policies/deployments and evaluating CA operations is less straightforward, but just as important for securing the web PKI. This dissertation is one of the first attempts to overcome trust management opacity. By observing new measurement perspectives and developing novel fingerprinting techniques, we discover the CAs that operate trust anchors, the default trust anchors that popular TLS user agents rely on, and a general class of injected trust anchors: TLS interceptors. This research not only facilitates new ecosystem visibility, it also provides an empirical grounding for trust management specification and evaluation. Furthermore, our findings point to many instances of questionable, and sometimes broken, security practices such as improperly identified CAs, inadvertent and overly permissive trust, and trivially exploitable injected trust. We argue that most of these issues stem from inadequate transparency, and that explicit mechanisms for linking trust anchors and root stores to their origins would help remedy these problems

Cinderella: Turning Shabby X.509 Certificates into Elegant Anonymous Credentials with the Magic of Verifiable Computation

Abstract-Despite advances in security engineering, authentication in applications such as email and the Web still primarily relies on the X.509 public key infrastructure introduced in 1988. This PKI has many issues but is nearly impossible to replace. Leveraging recent progress in verifiable computation, we propose a novel use of existing X.509 certificates and infrastructure. Instead of receiving & validating chains of certificates, our applications receive & verify proofs of their knowledge, their validity, and their compliance with application policies. This yields smaller messages (by omitting certificates), stronger privacy (by hiding certificate contents), and stronger integrity (by embedding additional checks, e.g. for revocation). X.509 certificate validation is famously complex and errorprone, as it involves parsing ASN.1 data structures and interpreting them against diverse application policies. To manage this diversity, we propose a new format for writing application policies by composing X.509 templates, and we provide a template compiler that generates C code for validating certificates within a given policy. We then use the Geppetto cryptographic compiler to produce a zero-knowledge verifiable computation scheme for that policy. To optimize the resulting scheme, we develop new C libraries for RSA-PKCS#1 signatures and ASN.1 parsing, carefully tailored for cryptographic verifiability. We evaluate our approach by providing two real-world applications of verifiable computation: a drop-in replacement for certificates within TLS; and access control for the Helios voting protocol. For TLS, we support fine-grained validation policies, with revocation checking and selective disclosure of certificate contents, effectively turning X.509 certificates into anonymous credentials. For Helios, we obtain additional privacy and verifiability guarantees for voters equipped with X.509 certificates, such as those readily available from some national ID cards

TLS/PKI Challenges and certificate pinning techniques for IoT and M2M secure communications

Transport Layer Security is becoming the de facto standard to provide end-to-end security in the current Internet. IoT and M2M scenarios are not an exception since TLS is also being adopted there. The ability of TLS for negotiating any security parameter, its flexibility and extensibility are responsible for its wide adoption but also for several attacks. Moreover, as it relies on Public Key Infrastructure (PKI) for authentication, it is also affected by PKI problems. Considering the advent of IoT/M2M scenarios and their particularities, it is necessary to have a closer look at TLS history to evaluate the potential challenges of using TLS and PKI in these scenarios. According to this, the article provides a deep revision of several security aspects of TLS and PKI, with a particular focus on current Certificate Pinning solutions in order to illustrate the potential problems that should be addressed

Practical Implementation of the Virtual Organization Cluster Model

Virtualization has great potential in the realm of scientific computing because of its inherent advantages with regard to environment customization and isolation. Virtualization technology is not without it\u27s downsides, most notably, increased computational overhead. This thesis introduces the operating mechanisms of grid technologies in general, and the Open Science Grid in particular, including a discussion of general organization and specific software implementation. A model for utilization of virtualization resources with separate administrative domains for the virtual machines (VMs) and the physical resources is then presented. Two well-known virtual machine monitors, Xen and the Kernel-based Virtual Machine (KVM), are introduced and a performance analysis conducted. The High-Performance Computing Challenge (HPCC) benchmark suite is used in conjunction with independent High-Performance Linpack (HPL) trials in order to analyze specific performance issues. Xen was found to introduce much lower performance overhead than KVM, however, KVM retains advantages with regard to ease of deployment, both of the VMM itself and of the VM images. KVM\u27s snapshot mode is of special interest, as it allows multiple VMs to be instantiated from a single image located on a network store. With virtualization overhead shown to be acceptable for high-throughput computing tasks, the Virtual Organization Cluster (VOC) Model was implemented as a prototype. Dynamic scaling and multi-site scheduling extensions were also successfully implemented using this prototype. It is also shown that traditional overlay networks have scaling issues and that a new approach to wide-area scheduling is needed. The use of XMPP messaging and the Google App Engine service to implement a virtual machine monitoring system is presented. Detailed discussions of the relevant sections of the XMPP protocol and libraries are presented. XMPP is found to be a good choice for sending status information due to its inherent advantages in a bandwidth-limited NAT environment. Thus, it is concluded that the VOC Model is a practical way to implement virtualization of high-throughput computing tasks. Smaller VOCs may take advantage of traditional overlay networks whereas larger VOCs need an alternative approach to scheduling

Greenpass Client Tools for Delegated Authorization in Wireless Networks

Dartmouth\u27s Greenpass project seeks to provide strong access control to a wireless network while simultaneously providing flexible guest access; to do so, it augments the Wi-Fi Alliance\u27s existing WPA standard, which offers sufficiently strong user authentication and access control, with authorization based on SPKI certificates. SPKI allows certain local users to delegate network access to guests by issuing certificates that state, in essence, he should get access because I said it\u27s okay. The Greenpass RADIUS server described in Kim\u27s thesis [55] performs an authorization check based on such statements so that guests can obtain network access without requiring a busy network administrator to set up new accounts in a centralized database. To our knowledge, Greenpass is the first working delegation-based solution to Wi-Fi access control. My thesis describes the Greenpass client tools, which allow a guest to introduce himself to a delegator and allow the delegator to issue a new SPKI certificate to the guest. The guest does not need custom client software to introduce himself or to connect to the Wi-Fi network. The guest and delegator communicate using a set of Web applications. The guest obtains a temporary key pair and X.509 certificate if needed, then sends his public key value to a Web server we provide. The delegator looks up her guest\u27s public key and runs a Java applet that lets her verify her guests\u27 identity using visual hashing and issue a new SPKI certificate to him. The guest\u27s new certificate chain is stored as an HTTP cookie to enable him to push it to an authorization server at a later time. I also describe how Greenpass can be extended to control access to a virtual private network (VPN) and suggest several interesting future research and development directions that could build on this work.My thesis describes the Greenpass client tools, which allow a guest to introduce himself to a delegator and allow the delegator to issue a new SPKI certificate to the guest. The guest does not need custom client software to introduce himself or to connect to the Wi-Fi network. The guest and delegator communicate using a set of Web applications. The guest obtains a temporary key pair and X.509 certificate if needed, then sends his public key value to a Web server we provide. The delegator looks up her guest\u27s public key and runs a Java applet that lets her verify her guests\u27 identity using visual hashing and issue a new SPKI certificate to him. The guest\u27s new certificate chain is stored as an HTTP cookie to enable him to push it to an authorization server at a later time. I also describe how Greenpass can be extended to control access to a virtual private network (VPN) and suggest several interesting future research and development directions that could build on this work