A Secure Payment Scheme Using RFID Technique for Retailing Services

Transcription

1 A Secure Payment Scheme Using RFID Technique for Retailing Services Chun-Ta Li 1, Cheng-Chi Lee 2,3,, Chi-Yao Weng 4,, and Chun-I Fan 4 1 Department of Information Management, Tainan University of Technology, 529 Zhongzheng Road, Tainan City 71002, TAIWAN (R.O.C.) th0040@mail.tut.edu.tw 2 Department of Library and Information Science, Fu Jen Catholic University, 510 Jhongjheng Road, New Taipei City 24205, TAIWAN (R.O.C.) 3 Department of Photonics & Communication Engineering, Asia University, 500 Lioufeng Road, Taichung City, TAIWAN (R.O.C.) Corresponding author s cclee@mail.fju.edu.tw 4 Department of Computer Science and Engineering, National Sun Yat-sen University, 70 Lienhai Road, Kaohsiung City 80424, TAIWAN (R.O.C.) cyweng@mail.cse.nsysu.edu.tw Abstract. For retailing services in Taiwan, icash is now often used in place of cash payment and it will save customer a lot of time and procedure for collecting ready money. However, in this article, we point out that icash is no prerequisite to revoke the lost/stolen/broken icash card and the savings money in icash card is equated to lose cash. Moreover, icash does not allow the customer to inquire about his/her historically transactions. Therefore, we propose an enhanced scheme for retailing services and this proposed macro-payment scheme benefits from combining RFID techniques and password verification to ensure deliberate commercial interaction. Keywords: Retailing services; Payment; RFID; Security. 1 Introduction Convenience stores (CVS) become more and more significant in grocery retailing applications [2]. Up to now, there are more than 9,300 convenience stores in Taiwan. A CVS is provided with on-the-spot sale, agency receipt, and services to purchase in advance. With payment model, customer pays for his/her purchase by cash payment or pre-paid card payment. For pre-paid card payment in Taiwan, President Chain Store Corporation (PCSC) [3] issued a pre-paid IC card, called icash [1]. icash is suitable for micro-payment and it is now often used in place of cash payment due to it will save customer a lot of time and procedure for collecting ready money. In the following, we shall present some advantages of icash as follows: Customer does not need to carry much small money or ready money with him/her. 36

2 2 Chun-Ta Li et al. Customer will save a lot of time and procedure for cash change. Customer has a very good collection of commemorative cards such as Hello Kitty card and Disneyland card. CVS gives a special discount for icash payment. icash payment can accumulate a bonus for exchanging some merchandize. However, icash is a bearer card and it is issued by PCSC without signature. Therefore, in case of a customer inadvertently lost or broken his/her icash card or customer s icash card is stolen by an adversary, the savings money in icash card is equated to lose cash. For this reason, there should be provision in the payment system invalidating the future use of lost icash card, otherwise an adversary or a pick-up person can expend all icash card s savings money. Moreover, icash system does not allow the customer to inquire about his/her historically transactions and above functionality flaws decrease the utility rate of icash. To remedy these functionality flaws, we propose an enhanced payment scheme, which covers all the identified weaknesses of icash system and is more secure and efficient for practical retailing environments. 2 The Proposed Scheme In this section, we shall present our RFID-based macro-payment scheme. Some notations in Table 1 are used in the proposed scheme. There are five phases in our scheme including registration phase, payment phase, deposit savings money phase, change password phase, and update master key phase. In addition, five assumptions are used in the proposed scheme and shown as follows: The links between connected RFID devices are bidirectional and the channels between back-end system and checkout reader are secure. S and R i are capable of executing H( ) algorithm and XOR operations. Moreover, in the proposed scheme, the stored information of a tag-card is only altered by legal checkout reader after mutual authentication. The back-end system maintains a local transaction table (LTT) for a specific transaction and the format of LTT is (T ag ID i, T j, Balance j, DT, MS i ). An attacker has the ability to query a tag as a checkout reader and the ability to clone a payment-tag. However, he/she is unable to extract the secret information of the tag-card and intercept or modify a message over the air in real time. Two master keys (K 1, K 2 ), the hashing function H( ) of back-end system and passwords of corresponding payers are undisclosed to any others for securing all future authentications. 2.1 Registration Phase Before the payer logins to the macro-payment system, the payer needs to perform the following steps. 37

3 A Secure Payment Scheme Using RFID Technique for Retailing Services 3 Table 1. Notations used in the proposed scheme P i/r i/s Payer(Customer)/Checkout reader/back-end system (MS i, T ag ID i ) The identity of merchandize and tag-card P W i P i s password stored in his/her personal tag-card K 1 A master key shared between reader and tag-card and it is generated by S K 2 A master key only stored in checkout reader and it is generated by S H( ) A private and collision-avoidance one-way hashing function M j The amount of jth balance, where j = 1, 2, 3,... and M 0 = 0 Balance j The balance of jth transaction, where Balance j = M j H(M j K 2 ) DT The date and time for a transaction T j The amount of money for a transaction, where j = 1, 2, 3,... P/D The operation of Payment/Deposit UK/CP The operation of Update master key/change payment password r A random number generated by PRNG, where PRNG is a Pseudo-Random Number Generator and it is maintained by the checkout reader a b Concatenation of parameter a and b Step 1 : We assume a payer P i goes to the merchandize MS i and P i wants to apply for a tag-card. P i must register his/her personal information with the back-end system S. Then, P i offers his/her payment password P W i and savings the amount of money T 1 to S. Step 2 : S generates an unique T ag ID i and computes H(P W i K 1 ) for P i, where is XOR operation and K 1 is a master key maintained by S. Then, S maintains its local transaction table LT T = (T ag ID i, T 1, Balance 1 = M 1 H(M 1 K 2 ), DT, MS i ), where M 1 = M 0 + T 1. Step 3 : Finally, S stores (T ag ID i, K 1, Balance 1, H(P W i K 1 ), H( ), ) on P i s tag-card and issues it to P i in secure manner. 2.2 Payment Phase After shopping, we assume the amount of money is T j and P i buys with tag-card. The checkout reader R i and P i s tag-card will perform the following steps. Step 1 : First, R i generates a random number r and computes K = H(K 1 r). Step 2 : Then, R i sends (K, r, P ) to P i s tag-card, where P is the operation of payment. Step 3 : After receiving the messages from R i, P i s tag-card checks if the computed H(K 1 r) is the same as the received K. If it does not hold, P i s tag-card terminated this transaction. Otherwise, P i s tag-card confirms that R i is a legal checkout reader and computes A = H(P W i K 1 ) Step 4 : Then, P i s tag-card sends (A, T ag ID i, F ) to R i, where F = Balance j 1 38

4 4 Chun-Ta Li et al. Step 5 : After receiving the messages, R i requests P i to input the payment password P W i and computes B = H(P W i K 1 ) and C = A B = Step 6 : Next, R i checks if the computed H(T ag ID i r K 1 ) is the same as C. If it does not match, the transaction is terminated by R i. Otherwise, R i sends (T ag ID i, C, F ) to the back-end system for further checking. Step 7 : S computes C F and compares it with the stored Balance j 1. If two values are identical, S confirms that P i is verified by R i and records (T ag ID i, T j, Balance j, DT, MS i ) into LTT, where the balance of jth transaction Balance j = M j H(M j K 2 ) and M j = M j 1 T j. S returns the value Balance j to R i. Step 8 : R i sends Balance j to P i s tag-card. Step 9 : Finally, P i s tag-card replaces the old balance Balance j 1 with the new balance Balance j and the payment phase is end. 2.3 Deposit Savings Money Phase In this phase, we assume the amount of deposit savings money is T j and this phase is extremely similar to payment phase. The major differences between payment phase and deposit savings money phase are in Step 2 and Step 7. In Step 2 of deposit savings money phase, the checkout reader R i sends (K, r, D) to P i s tag-card, where D is the operation of deposit. In Step 7 of deposit savings money phase, S records (T ag ID i, T j, Balance j, DT, MS i ) into LTT and returns the value Balance j to R i, where the balance of jth transaction Balance j = M j H(M j K 2 ) and M j = M j 1 + T j. 2.4 Change Payment Password Phase When a payer P i wants to update his/her payment password P W i to a new payment password P Wi new, P i must go to the merchandize MS i and the checkout reader R i and P i s tag-card will perform the following steps. Step 1 : R i generates a random number r and computes K = H(K 1 r). Step 2 : R i sends (K, r, CP ) to P i s tag-card, where CP is the operation of change payment password. Step 3 : After receiving the messages from R i, P i s tag-card checks if the computed H(K 1 r) is the same as the received K. If it does not hold, P i s tag-card terminated this phase. Otherwise, P i s tag-card confirms that R i is a legal checkout reader and computes A = H(P W i K 1 ) Step 4 : P i s tag-card sends (A, T ag ID i ) to R i. Step 5 : After receiving the messages from P i s tag-card, R i requests P i to input the original payment password P W i and computes B = H(P W i K 1 ) and C = A B = Step 6 : R i further checks if the computed H(T ag ID i r K 1 ) is the same as C. If it does not hold, this phase is terminated by R i. Otherwise, R i requests P i to input the new payment password P W new i. 39

5 A Secure Payment Scheme Using RFID Technique for Retailing Services 5 Step 7 : R i computes D = H(P Wi new K 1 ) Step 8 : R i sends D to P i s tag-card. Step 9 : Finally, P i s tag-card computes D H(T ag ID i r K 1 ) = H(P Wi new K 1 ) and replaces the original payment password H(P W i K 1 ) with the new payment password H(P Wi new K 1 ) and the payment phase is end. 2.5 Update Master Key Phase In order to improve the security of our proposed macro-payment scheme, the payment system will periodically update original master keys K 1 and K 2 to new master keys K1 new and K2 new. P i must go to the merchandize MS i to update the information stored in his/her tag-card and the checkout reader R i and P i s tag-card will perform the following steps. Step 1 : First, R i generates a random number r and computes K = H(K 1 r). Step 2 : Then, R i sends (K, r, UK) to P i s tag-card, where UK is the operation of update master keys. Step 3 : After receiving the messages from R i, P i s tag-card checks if the computed H(K 1 r) is the same as the received K. If it does not hold, P i s tag-card terminated this transaction. Otherwise, P i s tag-card confirms that R i is a legal checkout reader and computes A = H(P W i K 1 ) Step 4 : Then, P i s tag-card sends (A, T ag ID i, F ) to R i, where F = Balance j 1 Step 5 : After receiving the messages, R i requests P i to input the payment password P W i and computes B = H(P W i K 1 ) and C = A B = Step 6 : Next, R i checks if the computed H(T ag ID i r K 1 ) is the same as C. If it does not match, the transaction is terminated by R i. Otherwise, R i sends (T ag ID i, C, F ) to the back-end system for further checking. Step 7 : S computes C F and compares it with the stored Balance j 1. If two values are identical, S confirms that P i is verified by R i and computes E = K1 new H(T ag ID i r K 1 ), Y = H(K1 new K 1 ), W = H(P W i K1 new ) H(P W i K 1 ) and Balance j = M j H(M j K2 new ). Then, S records (T ag ID i, T j, Balance j, DT, MS i ) into LTT, where the amount of money T j = 0, the balance of jth transaction Balance j = M j H(M j K2 new ) and M j = M j 1 T j. S returns the values (E, Y, W, Balance j ) to R i. Step 8 : R i sends the values (E, Y, W, Balance j ) to P i s tag-card. Step 9 : After receiving the values from R i, P i s tag-card computes K1 new = E H(T ag ID i r K 1 ) and checks if the computed H(K1 new K 1 ) is the same as Y. If it holds, P i s tag-card replaces the original master key K 1 with the new master key K1 new. Step 10 : P i s tag-card further computes H(P W i K1 new ) = W H(P W i K 1 ) and replaces H(P W i K 1 ) with H(P W i K1 new ). Step 11 : Finally, P i s tag-card replaces the original balance Balance j 1 with the new balance Balance j and this phase is end. 40

6 6 Chun-Ta Li et al. 3 Functionality Comparisons In this section, the functionality comparisons among icash system [1] and our proposed system are summarized in Table 2. From Table 2, only ours provides mutual authentication between the checkout reader and the payer s tag-card. Moreover, because of employing local transaction table, the proposed system not only allows payer to re-apply for a new tag-card if the payer lost his/her tag-cards but also allows payer to inquire his/her historical transactions. Finally, if the legal payer inadvertently lost his/her tag-card, the proposed system can prevent a pick-up person to expend all tag-card s balance because the pick-up person must pass the password verification. Table 2. Functionality comparisons of our system with icash system Functionality/System icash system [1] Proposed system Without password/verification tables YES YES Mutual authentication NO YES Password verification NO YES Freely change payment password NO YES Periodically update master key NO YES Prevent damage from card loss or card stealing NO YES Re-apply for a new tag-card if payer lost tag-cards NO YES 4 Conclusions In this article, a novel and efficient RFID-based macro-payment scheme is proposed. By comparison with existing icash system, the proposed system not only keeps good features (e.g. without maintaining security-sensitive tables, freely change passwords, low computation costs, re-apply for a new card, prevention of card loss or card stealing, periodically update secret information) but also provides mutual authentication because the characteristics of password verification. References 1. icash Praveen Kopalle, Dipayan Biswas, Pradeep K. Chintagunta, Jia Fan, Koen Pauwels, Brian T. Ratchford, and James A. Sills. Retailer Pricing and Competitive Effects. Journal of Retailing, 85(1):56 70, President Chain Store Corporation. 41