Alptekin Küpçü

Learn More
We consider the problem of efficiently proving the integrity of data stored at untrusted servers. In the provable data possession (PDP) model, the client preprocesses the data and then sends it to an untrusted server for storage, while keeping a small amount of meta-data. The client later asks the server to prove that the stored data has not been tampered(More)
Proofs of retrievability allow a client to store her data on a remote server (e.g., “in the cloud”) and periodically execute an efficient audit protocol to check that all of the data are being maintained correctly and can be recovered from the server. For efficiency, the computation and communication of the server and client during an audit protocol should(More)
Fairly exchanging digital content is an everyday problem. It has been shown that fair exchange cannot be done without a trusted third party (called the Arbiter). Yet, even with a trusted party, it is still non-trivial to come up with an efficient solution, especially one that can be used in a p2p file sharing system with a high volume of data exchanged. We(More)
Peer-to-peer systems have been proposed for a wide variety of applications, including file-sharing, web caching, distributed computation, cooperative backup, and onion routing. An important motivation for such systems is self-scaling. That is, increased participation increases the capacity of the system. Unfortunately, this property is at risk from selfish(More)
We describe different strategies a central authority, the boss, can use to distribute computation to untrusted contractors. Our problem is inspired by volunteer distributed computing projects such as SETI@home, which outsource computation to large numbers of participants. For many tasks, verifying a task's output requires as much work as computing it again;(More)
In recent years, many advances have been made in cryptography, as well as in the performance of communication networks and processors. As a result, many advanced cryptographic protocols are now efficient enough to be considered practical, yet research in the area remains largely theoretical and little work has been done to use these protocols in practice,(More)
With the growing trend toward using outsourced storage, the problem of efficiently checking and proving data integrity needs more consideration. Starting with PDP and POR schemes in 2007, many cryptography and security researchers have addressed the problem. After the first solutions for static data, dynamic versions were developed (e.g., DPDP). Researchers(More)
Trusted Third Parties (TTPs) are widely employed in various scenarios for providing fairness guarantees (e.g., in fair exchange or e-commerce protocols, including secure two-party computation), for distributing secrets (e.g., in authentication or secret-sharing protocols, as well as group signatures), and for creating trust (e.g., as certificate(More)
Next generation sensor network deployments are foreseen to be large infrastructures, with multiple concurrent tasks running on the same set of hardware. Applications will need standardized methods to access and integrate data from such heterogeneous sensor networks. Hence, a Federated Sensor Network (FSN) model can significantly simplify the development of(More)