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)
—Bilinear maps are popular cryptographic primitives which have been commonly used in various modern cryptographic protocols. However, the cost of computation for bilinear maps is expensive because of their realization using variants of Weil and Tate pairings of elliptic curves. Due to increasing availability of cloud computing services, devices with limited(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)
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)
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)
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)
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)
—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)
Several pairing-based cryptographic protocols are recently proposed with a wide variety of new novel applications including the ones in emerging technologies like cloud computing, internet of things (IoT), e-health systems and wearable technologies. There have been however a wide range of incorrect use of these primitives. The paper of Galbraith, Paterson,(More)