Mehmet Sabir Kiraz

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We present a protocol issue that arises with the use of oblivious transfer in the malicious case of several two-party computation protocols based on Yao’s garbled circuit. We describe this issue for a protocol by Pinkas (Eurocrypt 2003) and for the Fairplay protocol, and we discuss why this issue still persists for a recently suggested modification of the(More)
? In the 1980s, Yao presented a very efficient constant-round secure two-party computation protocol withstanding semi-honest adversaries, which is based on so-called garbled circuits. Later, several protocols based on garbled circuits covering malicious adversaries have been proposed. Only a few papers, however, discuss the fundamental property of fairness(More)
Radio Frequency Identification (RFID) systems are vulnerable to relay attacks (i.e., mafia, terrorist and distance frauds) when they are used for authentication purposes. Distance bounding protocols are particularly designed as a countermeasure against these attacks. These protocols aim to ensure that the tags are in a distant area by measuring the(More)
Radio Frequency Identification (RFID) is a technology increasingly used in many applications for object identification. Ownership transfer of RFID tags is also another important requirement for some applications. Namely, the owner of an RFID tag may be required to change several times during its life-cycle. For an ownership transfer, the server of the new(More)
Oblivious transfer (OT) is a powerful primitive in modern cryptography, often used in a context of semi-honest adversaries. Committed oblivious transfer (COT) is an enhancement involving the use of commitments, which can be used in many applications of OT covering particular malicious adversarial behavior. For OT, many protocols are known that cover the(More)
Reducing computational cost of cryptographic computations for resource-constrained devices is an active research area. One of the practical solutions is to securely outsource the computations to an external and more powerful cloud server. Modular exponentiations are the most expensive computation from the cryptographic point of view. Therefore, outsourcing(More)
One of the most important benefits of public cloud storage is outsourcing of management and maintenance with easy accessibility and retrievability over the internet. However, outsourcing data on the cloud brings new challenges such as integrity verification and privacy of data. More concretely, once the users outsource their data on the cloud they have no(More)
In Financial Cryptography 2013, Bringer, Chabanne and Patey proposed two cryptographic protocols for the computation of Hamming distance in the two-party setting. Their first scheme uses Oblivious Transfer and provides security in the semi-honest model. The other scheme uses Committed Oblivious Transfer (COT) and is claimed to provide full security in the(More)
Databases contain most valuable personal, economic, and government information. They are most desirable to the malicious adversaries and therefore, it is very critical to protect against all possible adversarial behavior. With the recent rapid growth in the availability and popularity of cloud services, many personal and business and government information(More)
This paper examines Vaudenay’s privacy model, which is one of the first and most complete privacy models that featured the notion of different privacy classes. We enhance this model by introducing two new generic adversary classes, k-strong and k-forward adversaries where the adversary is allowed to corrupt a tag at most k times. Moreover, we introduce an(More)