Online social networks (OSNs) suffer from forged messages. Current studies have typically been focused on the detection of forged messages and do not provide the analysis of the behaviors of message publishers and network strategies to suppress forged messages. This paper carries out the analysis by taking a game theoretic approach, where infinitely repeated games are constructed to capture the interactions between a publisher and a network administrator and suppress forged messages in OSNs. Critical conditions, under which the publisher is disincentivized to publish any forged messages, are identified in the absence and presence of misclassification on genuine messages. Closed-form expressions are established for the maximum number of forged messages that a malicious publisher could publish. Confirmed by the numerical results, the proposed infinitely repeated games reveal that forged messages can be suppressed by improving the payoffs for genuine messages, increasing the cost of bots, and/or reducing the payoffs for forged messages. The increasing detection probability of forged messages or decreasing misclassification probability of genuine messages also has a strong impact on the suppression of forged messages.

A major challenge in distributed mobile networks is network integrity, resulting from short link duration and severe transmission collisions. This paper analyzes the impact of link duration and transmission collisions on a range of on-the-fly authentication protocols, which operate based on predistributed keys and can instantly verify and forward messages. All unexpired messages within a link duration can be verified retrospectively, once the keys are matched on-the-air. We develop a new general 4D Markov model which, apart from the first three dimensions modeling a cycle of the protocols, is able to unprecedentedly capture unexpired messages between cycles in the fourth dimension. Validated by simulation, our analysis reveals that the on-the-fly authentication is efficient under short link duration, but is susceptible to transmission collisions. The authentication requires holistic cross-layer designs of retransmission and rekeying. The proposed model is able to facilitate the design of the protocol parameters, which allows the protocols to significantly outperform the state of the art.

Challenges of authentication in decentralized mobile networks arise from frequently changing topologies and unreliable contention-based transmissions. We propose a new protocol to speed up authentications, reduce communication costs, and support opportunistic routing under fast-changing topologies. Key pairs are predistributed across the network. Nodes that predistributed the same pair can instantly verify and route messages for each other in an opportunistic and cooperative fashion, combating fast-changing topologies. We also enable a node to increasingly combine unauthenticated messages and a new message for signature or message authentication code generation, while trying different keys on-the-fly. The messages can be verified altogether, once a key is matched. The communication overhead, thus, becomes independent of the number of keys tried. Closed-form expressions for authentication rate, delay, and throughput are derived through a new three-dimensional Markov model. Validated by simulations, analytical results corroborate the robustness of the proposed protocol against changing topologies, as well as the substantially improved resistance to collusion attacks, as compared with the state of the art.

The source-location privacy threat is one of the critical issues in Wireless Sensor Networks (WSNs). Adversaries may trace along the sensor traffic to hunt targets around source nodes. Previous works proposed dummy messages and network coding to eliminate time and content correlations. However, these proposed schemes may result in explosion of polluted and dummy messages, opening up vulnerability to active attackers. In this work, we propose pollution avoiding source location privacy preserving scheme PA-SLP. A probabilistic key predistribution is proposed to predistributed keys in nodes. It enables intermediate nodes to verify signatures and filter out dummy or polluted messages with a certain possibility. In PA-SLP, a triple type homomorphic signature algorithm is developed to detect and classify three message types with only one pair of asymmetric keys. PA-SLP is able to adjust key distribution parameters to balance network performance and privacy. Security analysis and simulation results demonstrate PA-SLP can resist traffic analysis and filter out polluted and dummy messages effectively.