Hindawi Publishing Corporation International Journal of Distributed Sensor Networks Volume 2014, Article ID 865869, 6 pages http://dx.doi.org/10.1155/2014/865869
Research Article User Access Control and Authentication System for VoIP Service in Mobile Communication Environments Ho-Kyung Yang,1 Jeong-Kyung Moon,2 Cheol-Rim Choi,3 and Hwang-Bin Ryou4 1
Defense Acquisition Program, Kwangwoon University, No. 447-1, Wolgye-dong, Nowon-gu, Seoul 139701, Republic of Korea Division of Information Technology Education, Sunmoon University, No. 100 Galsan-ri, Tangjeong-myeon, Asan-si 336708, Republic of Korea 3 Humanitas College, Kyung Hee University, No. 1 Hoegi-dong, Dongdaemun-gu, Seoul 130701, Republic of Korea 4 Department of Computer Science, Kwangwoon University, No. 447-1 Wolgye-dong, Nowon-gu, Seoul 139701, Republic of Korea 2
Correspondence should be addressed to Jeong-Kyung Moon;
[email protected] Received 12 October 2013; Accepted 27 December 2013; Published 13 February 2014 Academic Editor: Hwa-Young Jeong Copyright © 2014 Ho-Kyung Yang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. VoIP, which is used to transmit voice data on the Internet, is being welcomed as a replacement for the PSTN. In VoIP, voice data are converted to IP data and transmitted in an ordinary IP network. As a result, it is less expensive than the ordinary telephone network and has excellent scalability. With the increasing demand for VoIP services, problems are also occurring, namely, security vulnerabilities and degraded service quality. To address these issues, in this paper an AA (Attribute Authority) server is added to VoIP to design an authentication system with bolstered security and differentiated user access.
1. Introduction When it comes to multimedia techniques, as networking techniques advance, the link with the Internet—which connects the entire world—is accelerating. Demands on services such as video conference and VoIP (Voice over Internet Protocol), which use the same IP (Internet Protocol) network to deliver multimedia data, including audio and video data, are quickly increasing. The ubiquitous computing environment has become important, which allows users to connect to the network regardless of their location. Along with this, the sensor network environment is also increasingly becoming important, which is what ubiquitous computing is based on. As there is no need to predetermine the locations of sensor nodes in a wireless sensor network, the nodes can be placed at arbitrary locations, which is especially useful for applications involving difficult-to-reach areas and for disaster rescue. Although VoIP efficiently provides voice communication between nodes, for it gains greater use, a variety of services are needed. Examples of additional services include various types, including call transfer, call forwarding when busy or when there is no response, call reservation, call waiting, and
call filtering. As a signaling protocol of VoIP for users to register services that they want at any time using a simple way, SIP and H.323 in particular are getting the attention [1]. Although increase in the number of users is expected for VoIP, there can be various problems with the packet network from a security standpoint in the fact that anyone can access it as it is an open network. While a PSTN can attacked only by physically accessing it, when it comes to a VoIP even remote attackers can be easily alter signaling messages or wiretap voice packets. Standardization of the SIP began at the IETP by considering expandability, component reuse, and interoperability as key criteria. SIP provides secure messaging services using digest user authentication, TLS, and S/MIME. Media security is implemented by using SRTP (Secure RTP), which is currently being drafted. Although using a stable security model can secure security, there is a disadvantage that the quality is drastically reduced for users, making it inconvenient for use [2]. In this paper a system is designed that addresses security problems caused by the increase in the use of VoIP services and for providing discriminate services according to user
2 access privileges. This paper is organized as follows. Section 1 gives the introduction; Section 2 is on related research; Section 3 describes the proposed technique and system; Section 4 System configuration; Section 5 Implementation and Performance Analysis; and Section 6 gives the conclusions.
2. Related Research 2.1. VoIP. VoIP is a service that uses the packet network originally designed for data communications for Internet telephony. It is a communication service that converts voice data to Internet protocol data packets so that calls can be made over the ordinary telephone network. Compared to the traditional telephone network service, it is low cost, supports multiple users simultaneously over the cable, and is highly extensible. Some of the protocols used are SIP and H.323 [2, 3]. 2.2. PKI. Public Key Infrastructure (PKI) is a composite security system environment that provides encryption and e-signing using a public key algorithm. That is, in PKI, data sent and received are encrypted and decrypted using a public key and a private key. Furthermore, a digital certificate is used to authenticate users. Different types of certificates include X.509, SSL, SET, S/MIME, and IPSec. The most widely used type of certificate is the X.509. X.509 is an ITU-T standard specifying standard formats for certificates. The X.509 v3 certificate standard, which came into being in 1995, is being recognized as the de-facto standard for PKI. The certificate system is a means of obtaining security in e-transactions or distribution of information. Under the system, the user’s identity is checked, changes to information have to be confirmed, and user confidentiality is ensured. Data encryption schemes include the public key encryption and the private key encryption [4, 5]. 2.3. Attribute Certificate. The attribute certificate refers to a type of certificate that plays a special role according to the particular environment rather than the certificate for personal identification as information protection services of various purposes increase in e-commerce. This type of certificate is used only for a specific goal and has a shorter lifespan than certificates used for personal identification. It can be used along with personal identification certificates. It has diverse applications in many fields such as network access control, billing according to access to contents, and web page access control [6–8]. 2.4. APTEEN. APTEEN (Adaptive Periodic Threshold Energy Efficient sensor Network protocol) provides a hybrid network that, while minimizing limitations of a priori sensor networks and responsive sensor networks, leverages on the advantages of both of them. APTEEN is designed for time-critical situations: it regularly transmits data to the users, informing them of the overall situation of the network, and immediately responds to sudden changes in the network
International Journal of Distributed Sensor Networks status. The user can also set threshold values for count times and attributes, managing energy use [9]. 2.5. ECSE. In ECSE (An Efficient Clustering Scheme through Estimate in Centralized Hierarchical Routing Protocol) [10], locations and energy levels are transmitted in the same way as in LEACH-C [11], and it uses simulated annealing algorithm [12] to select clusters based on energy levels and chooses the CHs. All nodes are requested to transmit energy levels only during settings in the first and second rounds. Starting with the settings in the third round, all sensor nodes are not requested to transmit current energy levels again. This is because, when one round is finished, the amount of energy remaining in each of the nodes can be found out, so it can be calculated how much energy was consumed on average by CHs as well as by ordinary nodes.
3. Proposed Technique The following are the prerequisites for the proposed technique. (i) The AA server and KMS server go through authentication beforehand and know each other’s public key values. (ii) The user generates a public key and a private key based on the PKI authentication technique, registers the public key with the KMS server, and requests for a certificate to be issued. (iii) The KMS server includes the public key value of the ADD server when issuing the certificate. (iv) AA server, at the same time a function of the base station. 3.1. User Registration Process. This is the process of registering the user before using the service. The register server issues a user certificate and the location server stores this. The register server and the location server are physically at the same location. The user registration algorithm, in which the user is registered with the register server and the certificate issued, is as follows. 3.2. Service Operation Structure. Communication using SIP involves going through a call connection process, during which various pieces of information may be leaked such as sender/receiver information, encryption technique, and method of communication. Therefore a secure call setup is needed. An authentication server and a KMS server are added based on the SIP call setup in the existing VoIP environment for the authentication process. As shown in Figure 1, the servers authenticate each other beforehand and share their public key values. In the call setup stage, the sender first sends a hello message and its certificate to the proxy server, which checks the certificate, and sends a response message that messages have to be encrypted. The user sends an INVITE message by obtaining the public key of the proxy server from the response message for encryption. Before sending the
International Journal of Distributed Sensor Networks A proxy (register)
SIP terminal
Hello. Personal certificate Response message certificate INVITE message cipher text
3
AA server (Attribute Authority)
XKMS (redirect)
B proxy (register)
SIP terminal
INVITE message (cipher text) User certificate (A)
Attribute certificate User certificate (A) 302 moved temporarily User certificate (B)
INVITE message (cipher text). User certificate (A) User certificate (A) verified Attribute certificate (A) verified
INVITE
(100 trying) (100 trying)
(100 trying) 108 ringing 108 ringing
108 ringing 200 OK
200 OK 200 OK ACK ACK ACK
Figure 1: Data flow chart.
message, its public key is generated based on that public key. The proxy server sends to the AA server the INVITE message and a public key certificate that includes a random number R and a hash value (R). The user is identified using that certificate and the AA server sends the attribute certificate and the contents received from the proxy server. The SMS server receives that information, reviews the contents of the user certificate and the attribute certificate and sends the other party’s address value and certificate. The proxy server encrypts using the public key obtained from the other party’s certificate and sends it. The proxy server on the receive side does authentication of the sender at SMS. Also, the sender’s attribute certificate is verified at the AA server. When this process is complete, the proxy server sends a message to PSTN, and the telephone network sends the message using bell sounds. If the process is successfully complete, a response message of “200 OK” is sent to indicate the call has been connected. The sender sends “ACK” to indicate that the message has been received successfully. This completes the call connection. When secure call setup is complete, data transmission begins with the RTP protocol [13–15].
Besides the forwarding feature which simply delivers messages (see Algorithm 1) the proxy server includes a privilege control feature for controlling privileges in relation to issuance of attribute certificates and also a security module for providing security features. 4.2. AA Server. As shown in Algorithm 2, the AA (Attribute Authority) server checks the client’s privileges in the process of establishing a session prior to data transfer and issues the attribute certificate according to the privileges. It is a server that creates attribute certificates for managing clients’ privileges, and it manages user privileges. AA server, at the same time a function of the base station. 4.3. Redirect (SMS) Server. The redirect server includes the following features: searching information at the other address, verification of attribute certificates, management of different servers, and issuance of certificates for the servers (see Algorithm 3).
5. Implementation and Performance Analysis 4. System Configuration 4.1. Proxy Server. The proxy server is designed to physically include the register server (location server).
5.1. Test Environment. For implementation of the proposed system, the RedHat 9.0, gcc V3.2.2 compiler of Linux Kernel V2.4.20.8smp was used.
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International Journal of Distributed Sensor Networks
int Proxy Receive Property(USER user) { MESSAGEmsg; stringciphertext; string plaintext; if (Receive Message(ciphertext)) { plaintext = Descript Message(ciphertext); msg = parsing(plaintext) if (msg.protocol == “SIP”) { if (user == analysis Property(msg.property)) { msg.control = property process(user); Transmit Message(Encript Message(msg)); } }
} return FAIL;
}
Algorithm 1: Property certificate receive algorithm of proxy.
int AA Generate Property(User user) { MESSAGEmsg; string ciphertext; string plaintext; if (Receive Message(ciphertext)) { plaintext = Descript Message(ciphertext); msg = parsing(plaintext); if (user == msg.user) { Generate Property Certificate(user Key); Transmit Message(Encript Message(msg)); } } }
return FAIL;
Algorithm 2: Property certificate generate algorithm of AA server.
The library was implemented based on text using a header file called sip.h, which is freely provided on the Internet. TLS functionality was implemented using the openssl library. 5.2. Performance Analysis. This section describes the results of testing each of the following systems based on a test using a VoIP system based on the implemented SIP protocol: an ordinary VoIP system, a TLS applied system, and the proposed system. The tests were conducted based on the INVITE command which makes the CALL. It was assumed that account registration has been done.
5.2.1. Comparison of Response Times for Different Number of Times Packets Are Sent and Received. Figure 2 compares the response times for different number of INVITEs in the VoIP system. For a typical system, the average response time is 56 ms for 20 INVITE requests. As shown in the figure, although the proposed system had a longer response time than a typical unsecure system, it was shorter than a TLS system. 5.2.2. Comparison of Security Aspects of Each System (1) Confidentiality. According to Table 1, in the voice session tapping in the same network, the attacker can disguise himself as the receiver and receive packet information.
International Journal of Distributed Sensor Networks
5
int Redirect Property Decision() { MESSAGEmsg; string ciphertext; string plaintext;
}
if (Receive Message(ciphertext)) { plaintext = Descript Message(ciphertext); msg = parsing(plaintext); if (Property decision(msg.property) { if (Address Search(msg.user)) Transmit Message(Encript Message(msg)); } } return FAIL;
Algorithm 3: Property certificate decision algorithm of redirect.
(2) Integrity. The forged call in Table 2 is an attack that makes normal service not possible by sending a large number of forged INVITE messages in a short time. For an ordinary system, attack is possible because a forged message can arrive, but for a TLS based system or the proposed system, since there is a stage where the session is set up or the attribute certificate is verified before a message is received, the attack will not be valid. Also, although RTP packets can be inserted intermittently in order to make call difficult for the target of attack or cut it off altogether for an ordinary system, since the other two systems include encryption, even if RTP packets are received by the servicing port, packets that are not encrypted will not be recognized as normal packets. 5.2.3. Comparison of Advantages and Disadvantages of Each System. While the ordinary VoIP system has fast response speed and low load on the system, its level of security is poor, and as a result systems with TLS added have become almost a de facto standard. But while these systems have excellent level of security, as a TLS session has to be set up every time a session is set up for each server, response time is slow and there is a lot of load on the system compared to ordinary systems. For the proposed system, however, an adequate level of security is provided while having less load on the system than TLS based systems (Table 3).
300
Response time (ms)
For ordinary systems, tapping is possible because encryption is not used. For TLS based systems, however, as the session was not formed to begin with, receiving information itself is not possible. While ordinary systems can be wiretapped by receiving the subscriber identification of the SIP server, for TLS based systems or for the proposed system, as a public key-based certificate is used, as long as the private key is not known by the attacker, wiretapping is not possible.
250 200 150 100 50 0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 Transmission packet number (times) General system TLS based system Proposed system
Figure 2: The response time with the number of INVITE.
Table 1: The comparison of the secret.
General system TLS based system Proposed system
Intercepted voice sessions in the same network
Intercepted voice sessions by registration pirate of SIP server
Available Impossibility Partially
Available Partially Partially
Table 2: The comparison of the integrity. Forged call attempts Inserted through the attack RTP denial of a voice call General system TLS based system Proposed system
Available Impossibility Impossibility
Available Impossibility Impossibility
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International Journal of Distributed Sensor Networks Table 3: The comparison of each system’s merits and faults.
Advantages Disadvantages (i) Quick response time General system (ii) Less load on the Vulnerable to security system (i) Slow response time TLS based system Excellent security (ii) Much load on the system (i) User-specific access control Needs the attribute Proposed system (ii) Providing various setting step additional service (iii) Providing security
6. Conclusions The ubiquitous computing environment has become important, which allows users to connect to the network regardless of their location. Along with this, the sensor network environment is also increasingly becoming important, which is what ubiquitous computing is based on. As there is no need to predetermine the locations of sensor nodes in a wireless sensor network, the nodes can be placed at arbitrary locations, which is especially useful for applications involving difficultto-reach areas and for disaster rescue. For activation, which effectively provides voice calls between terminals, various services are required and VoIP development environment of these. VoIP, which is used to deliver voice data on the Internet, is being welcomed as a means of replacing the PSTN. In VoIP, voice data are converted to Internet protocol data packets so that they can be delivered in an ordinary IP network. Thus, compared to ordinary telephone networks, it is of low cost and highly extensible. As VoIP services gain more traction, problems started to appear in terms of QoS and security. In this paper an authentication system is designed which is made secure and provides differentiated services according to user access. It does this by adding an AA server to the VoIP sessions setup stage. For future work, ways to increase QoS would need to be studied.
Conflict of Interests The authors have no conflict of interests related to the conduct and reporting of this research.
References [1] RFC, 2617, “HTTP Authentication: Basic and Digest Access Authentication,” IETF, 1999. [2] RFC, 2402, “IP Authentication Header,” IETF IPSec WG, 1998. [3] RFC, 2246, “The TLS Prototol Version 1.0,” IETF TLS WG, 1999. [4] RFC, 2402, “IP Authentication Header,” IETF IPSec WG, 1998. [5] RFC, 3029, “Internet X. 509 Public Infrastructure Data Validation and Certification Server Profocols,” IETF PKIX Working Group, 2001. [6] RFC, 3261, SIP: Session Initiation Protocol, 2002.
[7] Session Initiation Protocol (SIP) Working Group, http://www .ietf.org/html.charters/sip-charter.html. [8] T. F. Smith and M. S. Waterman, “Identification of common molecular subsequences,” Journal of Molecular Biology, vol. 147, no. 1, pp. 195–197, 1981. [9] A. Manjeshqar and D. Agrawal, “APTEEN: a hybrid protocol for efficient routing and comprehensive information retrieval in wireless sensor network,” in Proceedings of the International Parallel and Distributed Processing Symposium (IPDPS ’02), April 2002. [10] E. Hao, K. L. Kelly, J. T. Hupp, and G. C. Schatz, “Synthesis of silver nanodisks using polystyrene mesospheres as templates,” Journal of the American Chemical Society, vol. 124, no. 51, pp. 15182–15183, 2002. [11] D. H. Gracias, J. Tien, T. L. Breen, C. Hsu, and G. M. Whitesides, “Forming electrical networks in three dimensions by selfassembly,” Science, vol. 289, no. 5482, pp. 1170–1172, 2000. [12] Y. Sun and Y. Xia, “Shape-controlled synthesis of gold and silver nanoparticles,” Science, vol. 298, no. 5601, pp. 2176–2179, 2002. [13] RFC 3261 Annotated, 2008, http://www.openstack.co.kr/voipprotocolstack/rfc3261.pdf. [14] M. Baugher, D. McGrew, M. Naslund, E. Carrara, and K. Norrman, “The secure real-time transport protocol,” IETF draftietf-avt-srtp-09.txt, 2004. [15] M. Bauhger and D. Wing, “SDP security descriptions for media streams,” IETF draft-ietf-mmusic-sdescriptions-01.txt, 2003.
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