IJCSNS International Journal of Computer Science and Network Security, VOL.10 No.8, August 2010 215 Manuscript received August 5, 2010 Manuscript revised August 20, 2010 Multiple RFID Tag/Reader Co – Existence Proof Based On Rabin Cryptosystem Aik Theng Tan 1 , Dahlan Abdullah 2 , Ronsen Purba 3 , Rahmat Budiarto 1 1 School of Computer Sciences, Universiti Sains Malaysia, Penang, Malaysia 2 Computer Center, Universitas Malikussalah, Acheh, Indonesia 3 STMIK Mikroskil, Medan, Indonesia Abstract There are a lot of multiple RFID tag co –existence proofs have been developed by previous researcher such as Yoking Proof [1], On Existence Proof for multiple RFID tag [2] and A Proposed Proof by Thiti et al [3].[1],[2],[3] are applying symmetric secret sharing key method for performing an authentication in between RFID tag and server. In this manuscript, we are going to propose asymmetric secret key algorithm such as Rabin cryptosystem for generating multiple RFID tag co –existence proof. The reasons asymmetric secret key algorithm has been proposed instead of symmetric secret sharing key are: 1) Provides for message authentication: Public key encryption allows the use of digital signatures which enables the recipient of a message to verify that the message is truly from a particular sender [6]. 2) Detection of tampering: The use of digital signatures in public key encryption allows the receiver to detect if the message was altered in transit. A digitally signed message cannot be modified without invalidating the signature [6]. For next following sub-chapters in this manuscript [1],[2],[3] and including our proposed method will be shown in more details the way on how they are applied for generating multiple RFID tag /reader co–existence proof and discussion for its security analysis. Keyword: Rabin Cryptosystem, Symmetric Secret Sharing Key, Asymmetric Secret Key, RFID – Radio Frequency Identification. 1. Introduction Rabin Cryptosystem has been developed by Micheal O’Rabin in 1979. The purpose this type of cryptosystem has been developed to enhance the security of encryption data. Rabin cryptosystem is classified as asymmetric secret key and only public key will be revealing out to public. The private keys will be kept in secret and only owner able to unlock an encryption and get back the origin plaintext. It is related to the difficulty of integer factorization. Unlike existing multiple RFID tag co –existence proofs such as [1], [2], [3], it is more on verification hash value and MAC value by applying symmetric secret sharing key approach. By applying Rabin cryptosystem for generating multiple RFID tag co –existence proof, it is not only revealed out robustness security in between symmetric secret sharing key versus asymmetric secret key for breaking an encryption but also to proof Rabin cryptosystem is hard to be attacked if only public key has been known. From paper [4], [5], there are few sketches of existing network flow have been carried out to identify whether existing multiple RFID tag co–existence proofs network flow such as [1],[2],[3] are able to apply for generating multiple RFID reader co–existence proof. As a result, tag independent each other network flow is identified suitable to apply for generating multiple RFID reader co–existence proof compare to tag dependent each other network flow because it is able to generate multiple RFID tag/reader co– existence proof under different kind of configurations RFID reader and tag. By applying Rabin cryptosystem for generating multiple RFID tag co–existence proof, consideration for above scenario has been taken note to ensure that multiple RFID reader co –existence proof can be generated as well by using same network flow. Sub-chapters in this manuscript are organized as follow. Section 2 (Yoking Proof), section 3 (On Existence Proof for Multiple RFID Tag), section 4 (A Proof Proposed by Thiti et al), section 5 (Our Proposed Proof) and section 6 (Security Analysis). At last will be the conclusion for this manuscript. 2. Yoking Proof for Multiple RFID Tags Figure 1 showed that Yoking Proof is applied for generating multiple RFID tag co-existence proof. The descriptions about the proof are as followed: 1) The server sends a random number r to reader. 2) The reader sends the random number r to tag A. 3) Tag A starts to generate a hash value ra applying xa on r and transmitting its back to reader. 4) Reader receives hash value from tag A and sending ra and r to tag B. Tag B generates hash value rb by applying xb on r and applying xb on ra for generating MAC mb. 5) mb and rb are sent to reader by tag B. 6) Reader sends rb to tag A and tag A applies xa on rb for generating MAC ma. 7) Finally, reader computes PAB= (A,B,ma,mb) and submits to server for verification