A new security architecture for mobile commerce
Michael Turega Chongyan Ren
Department of Computation
University of Manchester, Institute of Science and Technology (UMIST)
Sackville Street, Po Box 80, Manchester M60 1QD, UK
Abstract:The next generation network (NGN), possible using IPV6, will seamlessly combine broadband wireless networks and wired IP networks together. This convergence of mobile and wired IP access technology will provide new avenues for growth, creating more opportunities and attracting more users in mobile commerce. In this environment, end-to-end security become more and more important, its absence hinders the mass acceptance of m-commerce. Cryptography is the foundation of security in mobile commerce and traditionally, the RSA public key scheme is commonly used in e-service system to construct the security infrastructure. This paper proposes a security solution for mobile commerce systems based on the ECC (Elliptic Curve Cryptograph) and ECDSA (Elliptic Curve Digital Signature Algorithm) public key schemes in order to meet the new requirements of small computation machines in wireless environment. Also, because wireless access is intrinsically more unreliable than fixed access, there is a need for new transaction protocols to operate efficiently in this environment, in particular the need for a new non-repudiation protocol. This paper identifies the initial work in these areas.
Key words: mobile commerce, wireless/mobile access, ECC, security
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1Introduction
In recent years Internet technology has emerged as the major driving force for new developments in telecommunication areas, the Internet has also become part of people’s normal life. As the Internet goes mobile there will be a trend towards moving Internet applications onto mobile devices.
Mobile commerce is a natural result of mobile access will soon become commonplace [2]. New technologies will allow portable device to access the Internet more conveniently and faster, growth in wireless Internet access is expected to surpass the traditional fix Internet access in the near future. This has opened up tremendous opportunities in the mobile commerce market [7].
End-to-end Security and speed of information delivery are both main concerns in electronic commerce systems [3] [8]. Traditionally, the RSA public key scheme is used to construct the PKI (Public Key Infrastructure) and is now well accepted in fixed IP networks, It is however, not necessarily suitable for mobile commerce access via small and portable device such as mobile phones and Personal Data Assistants because of the constraints in these mobile device: a less powerful CPU, less memory, limitation on power consumption, etc. To solve the problem, in this paper, an ECC public key scheme is proposed providing equivalence in security but with a much shorter key length.
Mobile Internet access today is through existing wireless networks such as 2G GSM systems and 2.5G GPRS, providing good coverage in urban areas, but with limited bandwidth. Third generation CDMA systems potentially bring new communication properties into the mobile commerce transaction process, but as yet coverage is very sparse and the network is unproven in mass usage. The properties of wireless networks are related to the characteristics of the wireless environment (for example limited bandwidth, limited geographical coverage, long latency, less stability of connections, less predictable availability) [3] and call for a new transaction protocols (in particular payment and non-repudiation) which should be able to operate within the limitations of wireless networks.
This paper examines the prospect for mobile commerce; provides an analysis of security requirements and discussed the usability of the ECC public key scheme. Finally, an outline proposal for a secure mobile commerce model is presented.
2M commerce, new frontier
The advantages that Mobile Commerce brings in terms of convenience and time saved will inevitably lead to its increasing use. [5]
2.1: Telecommunication convergence
The development of existing and new telecommunication technologies, such as GPRS, UMTS, 3GPP, wireless LAN/WAN, means that mobile/wireless users can conveniently and seamlessly access Internet services. The Internet will continue to become more and more available and ubiquitous. Data and information based applications will play an ever increasingly important role in people’s lives. [1].
2.2: Mobile commerce, a new frontier
Electronic commerce, despite recent setbacks has matured and continues to see phenomenal growth. So far most e-commerce system development involves wired infrastructures which are inflexibility and inhibit use mainly to home or office. Fortunately, the possibility of making the Internet accessible via mobile telephones and PDAs has generated an avenue providing new and more convenient e-commerce: mobile commerce. We believe the combination of wireless communication networks together with ubiquitous IP networks will be a driving force to the growth in mobile commerce. [2]
Mobile commerce together with other new mobile applications will bring revolutionary (and as yet unclear) changes to people‘s lifestyle. In the same way that the mobile telephone has freed individuals from the tyranny of the fixed line, mobile commerce will free people from the fixed computer. Booking hotels, theatre tickets, placing a bet or most other e-commerce activities will become commonplace, occurring when the requirement arises, not saved up for a session in the office.
3Security issues in M Commerce
In order to be successful in mobile commerce, security measures must be strong enough to protect the user from illegal abuses and to win the confidence of the participated entities [5].
3.1: Security requirements in electronic commerce
In an e-commerce system, trust must be established between the user end and server end. In order to achieve trust the following security function must be achieved:
To ensure privacy of transmission content during the conference.
To ensure each party be able to authenticate its counterpart [5], to make sure the message received really from the trust counterpart.
To achieve end-to-end confidentiality and integrity during message transmission. [4]
To supply non-repudiation service, which prevent entities from denying the bargained business deal.
Therefore, in order to provide a reliable and security e-commerce system, privacy of the transmission, end-to-end confidential and integrity during message transmission; together with non-repudiation of a transaction should be guaranteed.
At present, PKI and CA system based on RSA public key scheme are widely used in fixed e-application systems. Most security protocols involve these technologies.
3.2: Problems of wireless computation device
Mobile commerce, should not only guarantee the e-commerce security properties, but should also take into account the new problems encountered. These are:
Constraints (Low memory, less powerful CPU and limitations on power consumption) of small computation machine [3] [4].
Time delays during a transaction. In general, the mobile user will require a rapid response because of the nature of the activity.
Bandwidth constraints using wireless Internet access
Unreliable and potentially intermittent network service
The above limitations of mobile Internet access by wireless device make the current crypto algorithms (RSA) and transaction protocols unsuitable for constructing a mobile commerce system security infrastructure. Hence direct secure services between mobile device and mobile commerce server can be problematical.
One current approach used today in mobile commerce systems is to adopt Agent Technology (figure 1). In agent-based systems, security is handled by the agent where messages sent by a mobile device are decrypted and re-encrypted (usually with SSL) before being sent to the mobile commerce server. Despite the connection between agent and web server being secure, the end-to-end security is compromised. This results in a serious deterrent for any organization considering a security-sensitive service for wireless user.
Fig.1 Agent based m commerce system
This leads us to consider an alternative security infrastructure.
Fig. 2 End-End m commerce system
3.3: Secure by ECC public key scheme
Elliptic Curve Cryptosystem (ECC) potentially provides equivalent security to RSA based systems but with a much shorter key length and ECC is becoming accepted as a viable alternative to the public-key cryptography algorithm RSA in small wireless computation device. [6]
The following (Table 1) is the key length comparison of ECC and RSA providing equivalent security.
Time to break in MIPS year / RSAKey size
(Bits) / ECC
Key size
(Bits) / RSA/ECC
Key size
Ratio
104 / 512 / 106 / 5:1
108 / 768 / 132 / 6:1
1011 / 1,024 / 160 / 7:1
1020 / 2,048 / 210 / 10:1
1078 / 21,000 / 600 / 35:1
Table 1. Key size equivalent strength comparison [9]
Table 2 shows the digital signature and verification timings for RSA and ECDSA
Operation / RSA-1024 (e=3) / ECDSA-168(Over GF (p))
Signature / 43 / 5
Verification / 0.6 / 19
Key Generation / 1100 / 7
Table 2. Digital signature timing (in milliseconds) on a 200MHZ Pentium Pro [9]
3.4: A non-repudiation m-commerce transaction protocol
The use of Digital Signature technology can guarantee that both participants in a transaction are who they say they are and also can prevent repudiation of a transaction.
Potential repudiation can however occur when the communication link fails during the two way confirmation process. This problem is exacerbated by a ‘less than perfect’ communications link. This is precisely the situation that can occur with mobile commerce. For example a mobile purchaser may click the purchase confirmation button immediately before the train he is travelling on enters a long tunnel and the link is lost. Did the transaction go through? Was payment taken? These are all relevant questions to both e-commerce and m-commerce is it simply a question of degree and the likelihood of this occurring. In a wireless/mobile access environment, the fact the user may be roving, intermittent coverage of the service or shielding (especially in built up areas) may result in short term or long term interruptions to the network service.
We recognise the need (perhaps not fully achievable) for a guaranteed non-repudiation protocol. Our initial work has started looking at peer to peer and agent based alternatives for providing this guarantee.
4A proposal of security solution
We present an outline proposal for a secure mobile commerce system which will overcome some of the shortcomings of existing system, in particular, the need for more efficient encryption and the need for an effective non-repudiation protocol. (Fig.3)
Fig. 3 Simple security m commerce architecture
First, it is assumed that the mobile user accesses the Internet via GPRS or 3G mobile communication networks. This theoretically guarantees a data rate of at least 160Kbps on GPRS and possibly much more on 3G although as yet the technology needs to prove itself in a busy urban environment.
SSL protocol based on PKI and CA architecture is proposed in order to establish an end-to-end secure tunnel between mobile users and mobile commerce service providers. ECC is proposed as the Public Key algorithm used to realise the CA certificate that means we use ECC instead of the traditional RSA Public Key algorithms. By using ECC, we gain equivalent security to RSA but with less memory usage and CPU consumption and at an increased speed [6].
In the application layer, a non-repudiation transaction protocol is proposed in order to enable sufficient trust between the participants to make m-commerce viable.
A security API library for applications would be implemented in the mobile device. The ECC key pair would be generated and the private key securely stored within the mobile device.
5Conclusion and future work
In this paper, we present a proposal for a secure mobile commerce infrastructure. We believe that the ECC public key scheme is suitable and beneficial to a security infrastructure for mobile commerce; it is easier and cheaper to implement security functions for small computational devices whilst still providing users and mobile commerce system providers with sufficient security and convenience.
Work is also progressing in the area on non-repudiation protocols and to this end we are undertaking practical experiments to determine the dynamic properties of mobile Internet access via GPRS, a prerequisite to specifying the requirements for the non-repudiation protocol.
References
[1] Lu, W.W.; “Compact multidimensional broadband wireless: the convergence of wireless mobile and access” IEEE Communications Magazine, Volume: 38 Issue: 11, Nov 2000 Page(s): 119 -123
[2] Varshney, U.; Vetter, R.J.; Kalakota, R.; “Mobile commerce: a new frontier” Computer, Volume: 33 Issue: 10, Oct 2000 Page(s): 32 –38
[3] Soriano, M.; Ponce, D.; “A security and usability proposal for mobile electronic commerce” IEEE Communications Magazine, Volume: 40 Issue: 8, Aug 2002 Page(s): 62 -67
[4] Hsiao-Kuang Wu; Shu-Ching Yang; Yung-Tai Lin; “The sharing session key component (SSKC) algorithm for end-to-end secure wireless communication” Security Technology, 2000. Proceedings, IEEE 34th Annual 2000 International arnahan Conference on, 2000 Page(s): 242 -250
[5] Van Thanh, D. “Security issues in mobile ecommerce” Database and Expert Systems applications, 2000. Proceedings, 11th international Workshop on, 2000 Page(s): 412 -425
[6] Omidyar, G.; “Internet services over mobile and wireless networks architectures and protocols” Universal Multiservice Networks, 2000, ECUMN 2000. 1st European Conference on, 2000 Page(s): 1-4
[7] Gupta, V.; Gupta, S.; “Securing the wireless Internet” IEEE Communications Magazine, Volume: 39 Issue: 12, Dec 2001 Page(s): 68 -74
[8] Liu, J.K.; Wei, V.K.; Siu, C.; Chan, R.L.; Choi, T.; “Multi-application smart card with elliptic curve cryptosystem certificate”EUROCON'2001, Trends in Communications, International Conference on. , Volume: 2, 2001
[9] E.; Emarah, A.E.; El-Shennawy, K.; Mohammed, “Elliptic curve cryptosystems on smart cards” Security Technology, 2001 IEEE 35th International Carnahan Conference on, Oct 2000
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