Showing papers by "Seny Kamara published in 2005"

Achieving efficient conjunctive keyword searches over encrypted data

Abstract: We present two provably secure and efficient schemes for performing conjunctive keyword searches over symmetrically encrypted data. Our first scheme is based on Shamir Secret Sharing and provides the most efficient search technique in this context to date. Although the size of its trapdoors is linear in the number of documents being searched, we empirically show that this overhead remains reasonable in practice. Nonetheless, to address this limitation we provide an alternative based on bilinear pairings that yields constant size trapdoors. This latter construction is not only asymptotically more efficient than previous secure conjunctive keyword search schemes in the symmetric setting, but incurs significantly less storage overhead. Additionally, unlike most previous work, our constructions are proven secure in the standard model.

Key Regression: Enabling Efficient Key Distribution for Secure Distributed Storage.

Abstract: The Plutus file system introduced the notion of key rotation as a means to derive a sequence of temporally-related keys from the most recent key. In this paper we show that, despite natural intuition to the contrary, key rotation schemes cannot generically be used to key other cryptographic objects; in fact, keying an encryption scheme with the output of a key rotation scheme can yield a composite system that is insecure. To address these shortcomings, we introduce a new cryptographic object called a key regression scheme, and we propose three constructions that are provably secure under standard cryptographic assumptions. We implement key regression in a secure file system and empirically show that key regression can significantly reduce the bandwidth requirements of a content publisher under realistic workloads using lazy revocation. Our experiments also serve as the first empirical evaluation of either a key rotation or key regression scheme.

An Extensible Platform for Evaluating Security Protocols

Abstract: We present a discrete-event network simulator, called Simnet, designed specifically for analyzing network-security protocols. The design and implementation is focused on simplicity of abstraction and extensibility. Moreover, its modular architecture allows operators to dynamically customize running simulations. To demonstrate its strengths we present cases studies that focus on examining security-centric problem domains. In particular, we present an analysis of worm propagation modeling for worms with varying target selection algorithms on topologies representing a few million hosts. Additionally, we examine the use of countermeasures such as aggregate congestion control as a defense against DDoS attacks, and present analysis for a variant called direct-pushback. Lastly, we provide an empirical analysis of the computational and bandwidth overhead induced by proposed security extensions to DNS. These experiments hopefully illustrate that Simnet is not only scalable and efficient, but provides a viable platform for prototyping and analyzing non-trivial security protocols - a task which we argue cannot be easily accomplished elsewhere.

Secret locking: exploring new approaches to biometric key encapsulation

Abstract: Biometrics play an increasingly important role in the context of access control techniques as they promise to overcome the problems of forgotten passwords or passwords that can be guessed easily.