Modular-based channel hopping (CH) rendezvous algorithms can provide guaranteed rendezvous for Cognitive Radio Networks (CRNs) without time synchronization or Common Control Channels (i.e., blind rendezvous). Recently, the Enhanced Jump-Stay (EJS) scheme [13] has been proposed that decreases the Maximum Time To Rendezvous (MTTR) and the Expected Time To Rendezvous (ETTR) for users with a different number of channels (asymmetric). We develop a Symmetric Channel Detecting Jamming (SCDJ) attack and a novel probabilistic Asymmetric Channel Detecting Jamming (ACDJ) attack that dramatically decrease the rendezvous success rates of EJS. Our simulation results show that ACDJ significantly reduces the rendezvous probability of the asymmetric EJS scheme. We analyze the Random rendezvous scheme for the asymmetric model and show it vastly outperforms asymmetric EJS under ACDJ. We also developed the Random Enhanced Jump Stay (REJS) rendezvous that guarantees MTTR, significantly decreases the Expected Time To Rendezvous (ETTR) of EJS, and, due to the random part, appears to be resistant to channel detecting jamming attacks. REJS appears to be uniformly better than EJS with major performance improvements and significantly smaller theoretical ETTR upper-bounds and similar positive simulation results.

Recently, blind rendezvous algorithms have been proposed for cognitive radio networks due to the limitations of centralized servers or common control channels. However, these algorithms are vulnerable to our Channel Detecting Jamming Attacks (CDJAs) where a jammer computes and jams their channel hopping sequences by utilizing the properties of each rendezvous scheme. We have demonstrated that CDJAs, with capabilities similar to normal users, can significantly reduce rendezvous success rates for the Modular Clock and Jump Stay symmetric blind rendezvous algorithms [11], [12]. Here, we extend our CDJAs to the Generated Orthogonal Sequence (GOS) [15] algorithms. Our CDJAs, with one/two listening channels, quickly determine the channel hopping sequence for the GOS algorithm. Corresponding simulation results show the rendezvous success rates of GOS and other efficient blind rendezvous algorithm dramatically decrease under CDJAs. We compare these results to the Random rendezvous algorithm and show Random vastly outperforms five efficient blind algorithms under CDJAs and in other measures as well. Our CDJA is a major security concern for the state-of-the-art symmetric blind rendezvous algorithms for cognitive radio networks.

Efficient utilization of wireless bandwidth is a critical, if not the key, component of the wireless network architectures that balance availability and access. Cognitive Radio Networks (CRNs) are an important part of the solution to this problem. Common control channels (CCCs) for rendezvous in CRNs have limitations such as single point of failure, low scalability, and susceptibility to jamming attacks. Several rendezvous algorithms have recently been proposed that remove the need for CCCs. In particular, the Modular Clock (MC) channel hopping rendezvous algorithms provide extremely efficient rendezvous times for CRNs without using time synchronization and CCCs (i.e., blind rendezvous). However, these algorithms are vulnerable to Sequence Sensing Jamming Attacks (SSJAs) in which the jammer can estimate the channel hopping sequences within the first-half period of the MC algorithm. Using a single jammer and two listening channels, we show how to compute the entire MC Channel Hopping (CH) sequence and thus reduce the rendezvous success rate from around 95% to around 15% for the basic period. We show this is a major security problem for CRNs utilizing the MC algorithm since any secondary user or even group of users can easily be denied access to the network with high probability. We also compare these results to the Random rendezvous algorithm and show it vastly outperforms the MC algorithm when there are security concerns about a sequence sensing jammer.

Recently many channel hopping algorithms have been studied to guarantee rendezvous for Cognitive Radio Networks (CRNs). These algorithms propose rendezvous methods without using common control channels (CCCs) to avoid the limitations such as single point of failure, low scalability, and jamming attacks. In particular, the Jump-Stay based channel hopping rendezvous (JSR) algorithms provide guaranteed rendezvous for CRNs with no time synchronization or CCCs (i.e., blind rendezvous). However, the JSR algorithms are still vulnerable to Channel Detecting Jamming Attacks (CDJAs) in which the jammer can estimate the channel hopping sequences within the first jump-pattern. The jammer can compute the entire JSR channel hopping sequence and thus reduce the rendezvous success rate from 100% to less than 20% and 10% using one and two listening channels respectively. To mitigate this problem, we revisit both the Random rendezvous scheme and the Role-based Channel Rendezvous (RCR) scheme extended from role- based rendezvous algorithms to increase the probability of the rendezvous against the CDJAs. We also compare the JSR algorithm to both the Random and RCR algorithms and show the Random and RCR vastly outperform the JSR algorithm when there are security concerns about a channel detecting jammer. Especially, the effectiveness of CDJA is negligible for the Random and RCR schemes but their expected time to rendezvous (TTR) is close to the JSR's expected TTR.

Researchers have recently studied random spread spectrum techniques to protect the wireless broadcast communications from reactive jamming attacks in traditional Direct Sequence Spread Spectrum (DSSS) networks. They proposed mechanisms to eliminate the pre-shared key vulnerability by generating different code sequences for each message using random seeds and disclosing the seeds at the end of the message. In this paper, we present a new type of jamming attack called a seed jamming attack for the fixed message size and these seed disclosure schemes are vulnerable to it. The seed jamming attack focuses on jamming any part of the random seeds of the messages. Their sizes are relatively small and their position in messages is known to the public a priori. Thus, the receivers cannot despread any part of the messages due to the failure of regenerating proper code sequences with the corrupted seed. Jamming the seed precludes the use of any possible FEC since the receiver cannot decode any bits in the message. To overcome the seed attack, we propose an advanced random seed DSSS (ARS-DSSS) scheme which strengthens the previous algorithm called DSD-DSSS [4] by using an additional location seed. The new seed avoids the seed jamming attack by using variable message sizes instead of using known fixed message sizes while incurring almost no additional performance overhead. Our security analysis and implementation results demonstrate how to defeat the seed jamming attacks and how to reduce the computation overhead of DSD-DSSS from the cardinality of seed code set Ceto 1.

A wireless sensor network is expected to consist of a potentially large number of low-cost, low-power, and multi-functional sensor nodes that communicate over short distances through wireless links. Due to their potential to provide fine-grained sensing and actuation at a reasonable cost, wireless sensor networks are considered ideal candidates for a wide range of applications, such as industry monitoring, data acquisition in hazardous environments, and military operations.