Abstract: Session Initiation Protocol (SIP), which is becoming the de facto standard for the next-generation VoIP networks, is currently receiving much attention in many aspects. One aspect which was not deeply addressed in the original SIP is the authentication procedure in SIP. Apart from its security, an SIP authentication protocol should be efficient. For VoIP services to replace traditional PSTN ones, they have to offer enough security and QoS. This paper proposes a robust and efficient three-party SIP authentication protocol. In this protocol, the end users are authenticated with the proxy server in their domain using the registrar server. In comparison with the previous works, our proposed protocol is more efficient and secure. To support our protocol with a formal security proof, a model is constructed using the high-level formal language (HLPSL). The model is verified using the model checking tool AVISPA and the result reports the protocol to be a safe one.
Abstract: Instances of batch traffic can be seen in many applications. A set of sensors around the source of a sudden event which try to report it to the cluster head and energy conserving MAC protocols in hierarchical networks with sleep-awake schedules which lead to burst traffics toward a single destination might be good examples. The transient non-stationary nature of network reaction to batch arrivals has led to the development of complex models in order to estimate the network quantities of interest. In this paper, we propose a non-stationary Markov model to capture the transient characteristics of IEEE 802.15.4-based networks response to batch traffic arrivals of one-shot type. Mainly, the slotted CSMA/CA MAC protocol of the IEEE 802.15.4 standard is analyzed and the packet loss metric value is extracted from the proposed model. Extensive simulations were conducted to evaluate the accuracy of the proposed model and to compare its performance with that of the previous models.
Abstract: There have been trends in using spread spectrum channel accessing techniques in wireless sensor networks to mitigate the effect of potential collisions in concurrent transmissions and to increase the throughput as well as countering jamming-like noises. Overhearing of the data has been previously analyzed in cellular CDMA networks as this technique was first introduced for mobile communications with multiple transmitting users sending their data to a single base station which controls their transmission power. But sensor (and ad hoc) networks are usually devoid of any coordinating devices and the transmission is usually done toward different local destinations using distributed power controlling methods. This paper provides a systematic analysis of overhearing performance in low-traffic sensor networks especially when the sensing point is located somewhere at the middle of the network which is not necessarily near the sink. The distributed code assignment which is a key issue in infrastructureless CDMA networks has been taken into account in the development of a theoretical model. The result of this analysis shows that the higher the number of used codes, the higher is the gain of overhearing. Thus using this parameter, the network designer has statistical control over the amount of potential overheard data. We have also developed simulations of the proposed model and the results support the predictions of the theoretical model.
Abstract: Wireless sensor networks, applied for monitoring physical environments, have recently emerged as an important application of the ad hoc networks paradigm. Low processing power and wireless connectivity make such networks vulnerable to various types of attacks. The dense deployment of sensors along with the protocol deficiencies, make broadcast attacks feasible. The current solutions for these types of attacks are mainly cryptographic and suffer from either heavy computational complexity or lack of mobility support. In this paper we propose an energy efficient method to fortify sensor networks against broadcast attacks using some key features of such networks like small transmission range and low reception-sensitivity. The main idea relies on modifying the reply timings of current MAC sub-layer protocols and embedding a two or three-way handshake protocol in broadcast scenarios so that the adversary receives a negative feedback from the network in response to his greediness in infecting nodes. The simulations confirm the efficiency of this countermeasure applied to the IEEE 802.15.4.
Abstract: High expense of satellite channels along with providing telephony services for rural regions makes us to propose a new medium access control (MAC) protocol for sending signaling of telephony traffic via geo stationary satellite with narrow bandwidth channels. This paper explores an efficient MAC protocol, slot reservation demand assignment multiple access (SRDAMA), and also examines its performance via ns-2.31 simulator. It is notable that for simulation of this scheme some changes has been made to C++ codes of ns-2.31. To best of our knowledge no previous work has studied the problem of transmitting telephony traffic signaling over narrow bandwidth geo satellite channel.
Abstract: Performance of multi-hop ad hoc networks is highly affected by the hidden and exposed node problems. The RTS/CTS handshaking protocol used in the IEEE 802.11 standard was designed to solve the hidden node problem; however it was not successful in thoroughly eradicating the problem. We claim that it is sometimes possible to earn more throughput by controlling or even wisely creating this phenomenon. We suggest a solution to improve the throughput in IEEE 802.11-based multi-hop ad hoc networks by modifying the NAV mechanism. In our approach every node controls the packet transmission decision-making through a set of fuzzy-like rules which are based on the node queue level and environment variables. Simulation results show that our approach increases the overall throughput of the network in multi-hop scenarios.
Abstract: An invisible image watermarking scheme tends to insert
the mark in a transparent manner, with the highest
possible energy. Several watermarking algorithms use
human visual models as perceptual masks to maximize the
power of watermark. We take advantage of inhibitory and
excitatory characteristics of eye receptors which yield an
extra capacity, for amplifying watermark power, while
still satisfying imperceptibility constraint. Spatial-domain
image entropy is used as a measure of strength of
inhibitory effect. The principle of our idea is based on the
decomposition of mark sequence into two parts,
corresponding to two complementary sets of pixels in
spatial-domain. These sets are determined with respect to
two non-overlapping entropy intervals. We introduce
entropy masking as a post-amplification process, which
enables us to achieve exact localization. We derive
formulas to refine Watson’s visual model in a completely
different manner, with the assumption of having a priori
information about mark sequence. Simulation results of
the proposed model confirm the expected both energy
improvement and recovery enhancement of the watermark.
Abstract: Transparent, robust watermarking schemes tend to insert
invisible watermarks with the highest possible energy.
Singular values, in singular value decomposition (SVD),
are shown to be robust to intentional and unintentional
attacks. However, none of the algorithms proposed in the
literature considered the visual imperceptibility constraint
imposed by the human visual models. In this paper, we
introduce an optimal SVD-based embedding framework,
based on the well-known linear programming concept.
Given a binary sequence of the mark, we show how to
insert the message with the highest possible magnitude,
without outlawing the just noticeable thresholds driven by
the human visual system models in both spatial and linear
domains
