Ersin Uzun

Bio: Ersin Uzun is an academic researcher from PARC. The author has contributed to research in topics: The Internet & Encryption. The author has an hindex of 30, co-authored 104 publications receiving 4944 citations. Previous affiliations of Ersin Uzun include University of California & Bilkent University.

Bitter to Better — How to Make Bitcoin a Better Currency

Abstract: Bitcoin is a distributed digital currency which has attracted a substantial number of users. We perform an in-depth investigation to understand what made Bitcoin so successful, while decades of research on cryptographic e-cash has not lead to a large-scale deployment. We ask also how Bitcoin could become a good candidate for a long-lived stable currency. In doing so, we identify several issues and attacks of Bitcoin, and propose suitable techniques to address them.

Interest flooding attack and countermeasures in Named Data Networking

Abstract: Distributed Denial of Service (DDoS) attacks are an ongoing problem in today's Internet, where packets from a large number of compromised hosts thwart the paths to the victim site and/or overload the victim machines. In a newly proposed future Internet architecture, Named Data Networking (NDN), end users request desired data by sending Interest packets, and the network delivers Data packets upon request only, effectively eliminating many existing DDoS attacks. However, an NDN network can be subject to a new type of DDoS attack, namely Interest packet flooding. In this paper we investigate effective solutions to mitigate Interest flooding. We show that NDN's inherent properties of storing per packet state on each router and maintaining flow balance (i.e., one Interest packet retrieves at most one Data packet) provides the basis for effective DDoS mitigation algorithms. Our evaluation through simulations shows that the solution can quickly and effectively respond and mitigate Interest flooding.

A Reputation-based trust management system for P2P networks

Abstract: The open and anonymous nature of a P2P network makes it an ideal medium for attackers to spread malicious content. In this paper we describe a reputation-based trust management protocol for P2P networks where users rate the reliability of parties they deal with, and share this information with their peers. The protocol helps establish trust among good peers as well as identifying the malicious ones. Results of various simulation experiments show that the proposed system can be highly effective in preventing the spread of malicious content in P2P networks.

Needle in a Haystack: Mitigating Content Poisoning in Named-Data Networking

Abstract: Named-Data Networking (NDN) is a candidate next-generation Internet architecture designed to address some limitations of the current IP-based Internet. NDN uses the pull model for content distribution, whereby content is first explicitly requested before being delivered. Efficiency is obtained via router- based aggregation of closely spaced requests for popular content and content caching in routers. Although it reduces latency and increases bandwidth utilization, router caching makes the network susceptible to new cache-centric attacks, such as content poisoning. In this paper, we propose a ranking algorithm for cached content that allows routers to distinguish good and (likely) bad content. This ranking is based on statistics collected from consumers' actions following delivery of content objects. Experimental results support our assertion that the proposed ranking algorithm can effectively mitigate content poisoning attacks.

Loud and Clear: Human-Verifiable Authentication Based on Audio

Abstract: Secure pairing of electronic devices that lack any previous association is a challenging problem which has been considered in many contexts and in various flavors. In this paper, we investigate the use of audio for human-assisted authentication of previously un-associated devices. We develop and evaluate a system we call Loud-and-Clear (L&C) which places very little demand on the human user. L&C involves the use of a text-to-speech (TTS) engine for vocalizing a robust-sounding and syntactically-correct (English-like) sentence derived from the hash of a device’s public key. By coupling vocalization on one device with the display of the same information on another device, we demonstrate that L&C is suitable for secure device pairing (e.g., key exchange) and similar tasks. We also describe several common use cases, provide some performance data for our prototype implementation and discuss the security properties of L&C.

Named data networking

Abstract: Named Data Networking (NDN) is one of five projects funded by the U.S. National Science Foundation under its Future Internet Architecture Program. NDN has its roots in an earlier project, Content-Centric Networking (CCN), which Van Jacobson first publicly presented in 2006. The NDN project investigates Jacobson's proposed evolution from today's host-centric network architecture (IP) to a data-centric network architecture (NDN). This conceptually simple shift has far-reaching implications for how we design, develop, deploy, and use networks and applications. We describe the motivation and vision of this new architecture, and its basic components and operations. We also provide a snapshot of its current design, development status, and research challenges. More information about the project, including prototype implementations, publications, and annual reports, is available on named-data.net.

PORs: Proofs of Retrievability for Large Files

Abstract: In this paper, we define and explore proofs of retrievability (PORs). A POR scheme enables an archive or back-up service (prover) to produce a concise proof that a user (verifier) can retrieve a target file F, that is, that the archive retains and reliably transmits file data sufficient for the user to recover F in its entirety.A POR may be viewed as a kind of cryptographic proof of knowledge (POK), but one specially designed to handle a large file (or bitstring) F. We explore POR protocols here in which the communication costs, number of memory accesses for the prover, and storage requirements of the user (verifier) are small parameters essentially independent of the length of F. In addition to proposing new, practical POR constructions, we explore implementation considerations and optimizations that bear on previously explored, related schemes.In a POR, unlike a POK, neither the prover nor the verifier need actually have knowledge of F. PORs give rise to a new and unusual security definition whose formulation is another contribution of our work.We view PORs as an important tool for semi-trusted online archives. Existing cryptographic techniques help users ensure the privacy and integrity of files they retrieve. It is also natural, however, for users to want to verify that archives do not delete or modify files prior to retrieval. The goal of a POR is to accomplish these checks without users having to download the files themselves. A POR can also provide quality-of-service guarantees, i.e., show that a file is retrievable within a certain time bound.

A Survey of Information-Centric Networking Research

Abstract: The current Internet architecture was founded upon a host-centric communication model, which was appropriate for coping with the needs of the early Internet users. Internet usage has evolved however, with most users mainly interested in accessing (vast amounts of) information, irrespective of its physical location. This paradigm shift in the usage model of the Internet, along with the pressing needs for, among others, better security and mobility support, has led researchers into considering a radical change to the Internet architecture. In this direction, we have witnessed many research efforts investigating Information-Centric Networking (ICN) as a foundation upon which the Future Internet can be built. Our main aims in this survey are: (a) to identify the core functionalities of ICN architectures, (b) to describe the key ICN proposals in a tutorial manner, highlighting the similarities and differences among them with respect to those core functionalities, and (c) to identify the key weaknesses of ICN proposals and to outline the main unresolved research challenges in this area of networking research.

Zerocash: Decentralized Anonymous Payments from Bitcoin

Abstract: Bit coin is the first digital currency to see widespread adoption. While payments are conducted between pseudonyms, Bit coin cannot offer strong privacy guarantees: payment transactions are recorded in a public decentralized ledger, from which much information can be deduced. Zero coin (Miers et al., IEEE SaP 2013) tackles some of these privacy issues by unlinking transactions from the payment's origin. Yet, it still reveals payments' destinations and amounts, and is limited in functionality. In this paper, we construct a full-fledged ledger-based digital currency with strong privacy guarantees. Our results leverage recent advances in zero-knowledge Succinct Non-interactive Arguments of Knowledge (zk-SNARKs). First, we formulate and construct decentralized anonymous payment schemes (DAP schemes). A DAP scheme enables users to directly pay each other privately: the corresponding transaction hides the payment's origin, destination, and transferred amount. We provide formal definitions and proofs of the construction's security. Second, we build Zero cash, a practical instantiation of our DAP scheme construction. In Zero cash, transactions are less than 1 kB and take under 6 ms to verify - orders of magnitude more efficient than the less-anonymous Zero coin and competitive with plain Bit coin.