| Summary: | 碩士 === 國立中興大學 === 資訊科學系所 === 94 === Modern cryptology is largely based on Computational Complexity Theory. A realistic program corresponds to an algorithm or a Turing machine in the theory. An algorithm running in probabilistic polynomial time is considered to be a feasible method. For instance, for an encryption/decryption method, the decryption should not be accomplished in polynomial time without knowing the decryption key; for a digital signature, the signature should not be forged in polynomial time. The design of those cryptosystem usually needs primitives with some one-way property.
In this study, we investigate an important cryptographic primitive—pseudorandom functions. A pseudorandom function is designed to approximate a random function, that is, through querying a pseudorandom function and obtaining the function values, we cannot distinguish the function from a random function in polynomial time.
The result of this study can be divided into two parts. First, we analyze and improve a generic method of the construction of pseudorandom functions. Second, we use pseudorandom functions as components to design a practical protocol in the RFID system which is suitable for identifying merchandise. The proposed protocol is efficient and can resist tag counterfeiting and malicious tracing.
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