How to Break COT-Based Fingerprinting Schemes and Design New One

Digital fingerprinting schemes are cryptographic methods deterring buyers from illegally redistributing digital contents. It enables sellers to identify the traitor by providing each buyer with a slight different version. What is important in designing fingerprinting scheme is to make it more practical and efficient. Recently, two oblivious transfer protocolbased schemes to consider practicality were proposed. These are significant in the sense that they are completely specified from a computation point of view and are thus readily implementable. But these schemes cannot offer the security of sellers and buyers. In this paper, we show how to break the existing oblivious transfer-based fingerprinting schemes and then suggest how to make secure fingerprinting schemes against the dishonesty of sellers and buyers. We use oblivious transfer protocol with two-lock cryptosystem to make it practical and secure. All computations are performed efficiently and the security degree is strengthened in our proposal. key words: fingerprinting, committed oblivious transfer protocol, two-lock cryptosystem