Security is a serious bottleneck for the future of VoIP. Because of the time-critical nature of VoIP most of the same security measures currently implemented in today's data networks could not be used in VoIP networks. Two main factors affect voice traffic over secure IP channels. The first is the time required to encrypt payload and headers and the construction of the new ones. The second is the increased packet size because of the headers added to the original IP packet. Techniques that could be adopted to overcome these two problems in addition to the compression QoS issues associated with audio codecs put more strain on end-point CPU's. In this paper we propose a new QoS control scheme that uses a simple protocol to detect the end-point CPU capabilities, and according to this information, we choose dynamically the most suitable techniques for the transmission of voice over a secure IP channel to provide a superior QoS control performance, in terms of perceived speech quality.
Abstract-Compound MIMO wiretap channel with double sided uncertainty is considered under channel mean information model. In mean information model, channel variations are centered around its mean value which is fed back to the transmitter. We show that the worst case main channel is anti-parallel to the channel mean information resulting in an overall unit rank channel. Further, the worst eavesdropper channel is shown to be isotropic around its mean information. Accordingly, we provide the capacity achieving beamforming direction. We show that the saddle point property holds under mean information model, and thus, compound secrecy capacity equals to the worst case capacity over the class of uncertainty. Moreover, capacity achieving beamforming direction is found to require matrix inversion, thus, we derive the null steering (NS) beamforming as an alternative suboptimal solution that does not require matrix inversion. NS beamformer is in the direction orthogonal to the eavesdropper mean channel that maintains the maximum possible gain in mean main channel direction. Extensive computer simulation reveals that NS performs very close to the optimal solution. It also verifies that, NS beamforming outperforms both maximum ratio transmission (MRT) and zero forcing (ZF) beamforming approaches over the entire SNR range. Finally, An equivalence relation with MIMO wiretap channel in Rician fading environment is established.
The implementation of a wide, complex and varied networks, let the security development has great importance to the communication innovation. The advance encryption standard (AES) algorithm considered to be the leader of this innovation. A large variety of approaches for modifying AES have been appeared so as to satisfy the varying criteria of different applications [1]. Effort spent on evaluating AES security strength has been very limited, it is significant that the majority of researches at AES dealt with performance evaluation rather than with security evaluation [2]. The design and implementation of S-box are representing a key step in the AES algorithm [3]. So many efforts were emulated to redesign, reconstruct or renew the implementation of the S-boxes. In this paper, AES with Variable Mapping S-box (VMS-AES) is introduced. VMS-AES is a novel AES-like algorithm which uses the key data to generate parameter that used to shift (remapping) the substitution of S-box to another location randomly depend on the initial key and the derived sub keys data. The required modifications are being made for the inverse S-box mapping saving the non-linearity relationship between the S-box and its inverse. VMS-AES allows the change of the system parameters values (number of rounds, key size, chaining mode) then it presents the effects of these changes upon the security and Quality of service (QoS) which is the main objective of the recent work that evaluated the voice over IP (VoIP) security algorithms [4].
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.