– Operator-oriented model (Figure 9), where mobile operator offers mobile payment service using payment cards as source of payment issued by multiple banks or using personal accounts of mobile subscribers.
Figure 9: Operator-oriented MPS model
– Mixed model (Figure 10) with multiple banks and multiple operators.
An example of such model can serve an MPS working with international payment cards, for example, MasterCard or VISA. However, most perspective model is the National Mobile Payment System, being a part of the National Payment System, integrating all national banks and working with all mobile operators.
Figure 10: Mobile Payment System as a part of the National Payment System
4.4 Available payment means
The following payment means may be used as a source in the Mobile Payment System:
– Bank account
– Bank cards issued by local or global payment systems
– MNO subscribers personal accounts
4.5 Payment arrangement
Two operation types are available in MPS:
– Operations initiated by the Client
– Operations initiated by the Merchant
4.5.1 Operations initiated by the Client
Transactions initiated by the Client may contain the following steps:
1. By means of mobile device the Client generates a request containing parameters of the financial operation, payment instrument and secret PIN code
– Trusted Service Manager or broker providing a point of contact between service providers and MO
It is considered, that NFC payment systems can use credit cards as payment means for interactive shopping purchases via contactless NFC devices. After the payment transaction is processed successfully, result is stored in the system and sent to subscriber's handset. The use case is depicted in Figure 11 below. In order to actualise the scenario described above, following requirements are needed:
– User Authentication Communication security
– Protection of information stored, if mobile device is lost or stolen
– System storage to accumulate and process transaction records
Figure 11: Interactive shopping
NFC systems, due to its features, have become the most popular when carrying out the sale of consumer goods, and also within the transport sector, allowing for a reduction in the time spent to purchase tickets and significantly reducing lines for customers. Also, NFC-based systems can be successfully applied for authentication purposes instead of paper ID. Despite the differences, the main security methods for NFC operations remain the same as for remote services.
The most important requirement for payment systems, as well as e-government and e-health, including their mobile variations, is security, which is provided by meeting recommendations of the ITU Telecommunication Standardization Sector, which issued a manual entitled "Security in telecommunications and information technologies6". This manual provides an overview of existing ITUT Standards and their practical application in secure telecommunications. ITU-T Standards are required to follow, they stay as recommendations, but compliance with recommendations is essential to ensure compatibility and consistency of telecommunication systems of different countries.
Since these systems include many players, security considerations can be divided in multiple categories that include:
a) End-point Security
b) Mobile Application Security
c) Mobile Network Security
d) Identification of the requesting party that includes proper identification of the individual that is requesting the financial transaction.
Prior to the era of smart phones, management of mobile applications by operators on mobile phones was relatively easy. Basically, operators used to control which application can be downloaded onto device and their security characteristics. Management of mobile applications becomes more complicated with the advent of smart phones and ability to freely download third party applications. Nowadays, it is almost impossible to be completely certain that every application that is executing on a mobile device originated from a trusted source. As a result, mobile users are subject to additional threats such as identity theft, phishing, and loss of personal data.
The term "security" is used in the sense of minimising vulnerabilities of assets and resources. An asset is anything of value. Vulnerability is any weakness that could be exploited to violate a system or information it contains. A threat is a potential violation of security. The ITU-T Recommendation X.805 "Security Architecture for Systems Providing End-to-End Communications7" (Figure 10) of defines set of eight socalled "Security dimensions" – set of means that protect against all major security threats, described in the ITU-T Recommendation X.800 "Security architecture for Open Systems Interconnection for CCITT applications"0:
– destruction of information and/or other resources;
– corruption or modification of information;
– theft, removal or loss of information and/or other resources;
– information disclosure;
– service interruption.
Security dimensions are not limited to the network, but extend to applications and end user information as well. In addition, security dimensions apply to service providers or enterprises offering security services to their customers. The security dimensions are:
1) Access control;
4) Data confidentiality;
5) Communication security;
6) Data integrity;
Properly designed and implemented security dimensions support security policy that is defined for a particular network and facilitate the rules set by the security management.
The access control security dimension protects against unauthorized use of network resources. Access control ensures that only authorised personnel or devices are allowed to access network elements, stored information, information flows, services and applications. In addition, Role-Based Access Control (RBAC) provides different access levels to guarantee that individuals and devices can only gain access to, and perform operations on, network elements, stored information, and information flows that they are authorised for.
The authentication security dimension serves to confirm identities of communicating entities. Authentication ensures validity of claimed identities of entities participating in communication (e.g., person, device, service or application) and provides assurance that an entity is not attempting a masquerade or unauthorized replay of a previous communication.
The non-repudiation security dimension provides means for preventing an individual or entity from denying having performed a particular action related to data by making available proof of various network-related actions (such as proof of obligation, intent, or commitment; proof of data origin, proof of ownership, proof of resource use). It provides evidence that can be presented to a third party and used to prove that an event or action has taken place.
The data confidentiality security dimension protects data from unauthorized disclosure. Data confidentiality ensures that the data content cannot be understood by unauthorized entities. Encryption, access control lists and file permissions are methods often used to provide data confidentiality.
The communication security dimension ensures information flows exchange only between the authorised end points (information is not diverted or intercepted as it flows between these end points).
The data integrity security dimension ensures correctness or accuracy of data. The data is protected against unauthorized modification, deletion, creation, and replication and provides an indication of these unauthorized activities.
The availability security dimension ensures that there is no denial of authorised access to network elements, stored information, information flows, services and applications due to events impacting the network. Disaster recovery solutions are included in this category.
The privacy security dimension provides protection of information that might be derived from the observation of network activities. Examples of this information include web sites visited by a user, user geographic location, and IP addresses and DNS names of devices within service provider network.
In order to provide an end-to-end security solution, security dimensions must be applied to a hierarchy of network equipment and facility groupings, which are referred to as security Layers and security Planes. The Recommendation X.805 defines three security layers build on one another to provide network-based solutions:
– Infrastructure security Layer, consisting of network communication means and individual network elements (routers, switches, servers, communication lines);
– Services security Layer to protect service providers and their clients (both basic services – connection to resources, DNS, and additional services – VPN, QoS, etc.);
– Applications security Layer, includes 4 potential targets: application user, service provider, application provider, bounding software.
Security layers represent a series of interrelated factors that contribute to ensure network security: Infrastructure security layer allows to use Services security layer and Services security layer allows to use Applications security layer. Security architecture takes into account that each layer has different security vulnerabilities, and provides flexibility in reflexion of potential threats in the most appropriate way for a particular security layer.
Each of these security Layers consists of three security Planes, representing a specific type of network operation, protected by Security dimensions:
– End-User Plane;
– Control Plane;
– Management Plane.
Figure 12: X.805 – Security architecture for end-to-end network security
According to this Recommendation the security architecture logically divides the System in question into separate architectural components. This separation assumes a systematic approach to end-to-end security that can be used for planning of new security solutions as well as for assessing the security of the existing solutions. The security architecture addresses three essential questions with regard to the end-to-end security:
1) What kind of protection is needed and against what threats?
2) What are the distinct types of system equipment and facility groupings that need to be protected?
3) What are the distinct types of system activities that need to be protected?
These questions are addressed by three architectural components: security dimensions, security layers and security planes.
– Required security should be based on the use of:
– Means of identification and authentication of participants;
– Encryption of data transmitted through communication channels;
– Physical and administrative means to ensure the safety of information transmission and storage.
The ITU Recommendation X.11229 applies when using asymmetric cryptography, and provides guidelines for creation of secure mobile systems based on Public Key Infrastructure (PKI). This standard describes generation of public and private keys, certificate applications, as well as issuance, activation, use, revocation and renewal of the certificate.
The ITU Recommendations Y.2740 and Y.2741 describe security requirements and architecture of secured mobile financial transactions. These recommendations, though made for mobile remote financial transactions in NGN, are fully applicable to ensure security for m-Payment, m-Health and m-Government Systems in 2G, 3G and 4G mobile networks. The Recommendation Y.2741 describes the system architecture (Figure 5) and possible interaction scenarios. The example of such scenario for Merchant initiated payment is shown in Figure 11.
Figure 13: Performing payments initiated by merchant
The basic steps of the scenario are as follows:
1. a) the Merchant generates a payment offer and sends it to the MPS operator;
c) the request is sent to the client over the mobile operator channels.
2. The client receives the request through his/her mobile device and generates the response that contains the financial operation parameters as well as the parameters of the payment instrument;
3. The request is transmitted via the mobile operator channels;
4. The MPS operator receives the client's response;
5. Authentication of the client;
6. The required financial operation (remittance/payment) is performed using the client's payment instrument details;
7. The operation result is sent to the client;
8. The response is transmitted via the mobile operator channels;
9. The client receives the result of the financial operation.
The Recommendation Y.2740 defines four levels of system security and its provision. Security Level is determined by the extent to which security dimensions are implemented in the System. According to this Recommendation system participants should be aware of the Security Level, which should be stipulated in the participants’ agreement if it is not contrary to the law. Service providers can further reduce the risks by organizational means - to restrict the transfer of some information, to limit service for users with a low level of loyalty, etc. The System security is entrusted upon every participant of the System and is achieved by the physical and administrative facilities of security assurance at data transfer, processing and storage. Implementation of security dimensions are required to be executed by all the participants in respect of data involved in information exchange. Thus the subscribers are responsible for maintaining the secrecy of their PIN codes, for the safe storage of their mobile terminals, as well as for confidential information related to a bank account or plastic payment card secure parameters. In turn, service providers are liable for the logging of performed transactions, security of transmitted and stored sensitive information, user authentication, etc.
Security Levels defined in the ITU-T Recommendation Y.2740 "Security requirements for mobile remote financial transactions in next generation networks":
Security Level 1
System can rely on authentication provided by the NGN operator. Data confidentiality and integrity at their transfer are ensured by the data transfer environment (communications security), and at their storage and processing – by the data storage mechanism and System access control facilities. The privacy is ensured by the absence of sensitive data in the messages being transferred as well as by the implementation of the required mechanisms of data storage and the System access control facilities. The System components must not have latent possibilities of unauthorized data acquisition and transfer.
Security Level 2
Authentication when using the System services can be executed by using only one authentication factor and thus can be implemented without the application of cryptographic protocols. One-Time Password is used for authentication. One-Time Password is generated by means of various tokens (Single Factor OTP Device, Single Factor Cryptographic Device, etc.). Data confidentiality, integrity and privacy are ensured similarly to Level 1.
Security Level 3
Multifactor client authentication must be used to access System services. The Client shall use more than one authentication factor. Data confidentiality, integrity and privacy at message transmission must be ensured by using additional message encryption together with data transfer protocols that ensure the security of the data being transferred by the interoperation participants (including data integrity verification); at data storage and processing their confidentiality, integrity and privacy are ensured by additional mechanisms of encryption and masking, together with well-defined distribution of access in accordance with privileges and permissions.
To meet security requirements at this level, System shall use software modules installed in Clients' handsets. These modules shall implement at least two-factor authentication and ensure both encryption and decryption of transferred data. Each authentication shall require entry of the password or other activation data to activate the authentication key and the unencrypted copy of the authentication key shall be erased after each authentication (Multi-factor Software Cryptographic Token).
All System interoperation participants shall use security facilities that ensure the System against break-in. In the Level 3 solutions the security of data transferred over the communications channels shall be ensured by means of strong cryptography. The strength of a cryptographic method depends on the cryptographic key being used. Effective key size shall meet minimal length recommendations to suffice protection.
Security Level 4
This is the highest System security assurance level. To meet security requirements at this level, clients' mobile terminals shall be equipped with hardware security modules. Implementation of other security dimensions shall fully correspond to level 3. Both symmetric and asymmetric cryptographic algorithms may be applied to message encryption. To prevent interception or corruption of information between mobile terminal elements (e.g. CPU and display, CPU and keyboard), some security measures shall be taken to ensure the integrity of data exchange on the Client’s device (Trusted Execution Environment).
Security dimensions that are equally implemented at all Security Levels:
– access control,
– communication security,
The following security dimensions have different implementation at different Security Levels:
– data confidentiality,
– data integrity,
From Table 1 it follows that the implementation of the first and second levels of security can be achieved without installation of any special applications on the mobile device or special security element of mobile device; but to implement the third and fourth security levels, it is necessary to install custom applications that provide client authentication, encryption and decryption of data transmitted.
The access to every system component shall be granted only as provided by the System personnel or end-user access level.
Authentication in the System is ensured by the NGN data transfer environment
Single-factor authentication at the System services usage
Multi-factor authentication at the System services usage
In-person connection to services where personal data with obligatory identification is used.
Multi-factor authentication at the System services usage.
Obligatory usage of Hardware Cryptographic Module.
The impossibility of a transaction initiator or participant to deny his or her actions upon their completion is ensured by legally stated or reserved in mutual contracts means and accepted authentication mechanisms. All system personnel and end-user actions shall be logged. Event logs shall be change-proof and hold all actions of all users.
Data confidentiality during the data transfer, is ensured by the data transfer environment (communications security), and by the mechanism of data storage together with the means of system access control – at data storage and processing.
Data confidentiality during the data transfer is ensured by additional message encryption together with data transfer protocols that ensure the security of the data being transferred by the interoperation participants (including data integrity verification); at data storage and processing their confidentiality, integrity and privacy are ensured by additional mechanisms of encryption and masking together with well-defined distribution of access in concordance with privileges and permissions.
The implementation of the Level 3 requirements with the obligatory usage of hardware cryptographic and data security facilities on the Client’s side (Hardware Cryptographic module).
Privacy is ensured by the absence of sensitive data in the messages being transferred as well as by the implementation of the required mechanisms of data storage and the System access control facilities.
The System components must not have latent possibilities of unauthorized data acquisition and transfer.
The delivery of a message to the addressee is ensured as well as the security against unauthorized disclosure at time of transfer over the communications channels. It is ensured by the NGN communications providers.
It ensures that there is no denial of authorised access to the System data and services. Availability is assured by the NGN communications providers as well as the service providers