Dynamic Resource Optimization for Decentralized Estimation in Energy Harvesting IoT Networks

We study decentralized estimation of time-varying signals at a fusion center, when energy harvesting sensors transmit sampled data over rate-constrained links. We propose dynamic strategies to select radio parameters, sampling set, and harvested energy at each node, with the aim of estimating a time-varying signal while ensuring: i) accuracy of the recovery procedure, and ii) stability of the batteries around a prescribed operating level. The approach is based on stochastic optimization tools, which enable adaptive optimization without the need of apriori knowledge of the statistics of radio channels and energy arrivals processes. Numerical results validate the proposed approach for decentralized signal estimation under communication and energy constraints typical of Internet of Things (IoT) scenarios.Comment: Submitted to IEEE Internet of Things Journa

Contra-*: Mechanisms for Countering Spam Attacks on Blockchain's Memory Pools

Blockchain-based cryptocurrencies, such as Bitcoin, have seen on the rise in their popularity and value, making them a target to several forms of Denial-of-Service (DoS) attacks, and calling for a better understanding of their attack surface from both security and distributed systems standpoints. In this paper, and in the pursuit of understanding the attack surface of blockchains, we explore a new form of attack that can be carried out on the memory pools (mempools) and mainly targets blockchain-based cryptocurrencies. We study this attack on Bitcoin mempool and explore the attack effects on transactions fee paid by benign users. To counter this attack, this paper further proposes Contra-*:, a set of countermeasures utilizing fee, age, and size (thus, Contra-F, Contra-A, and Contra-S) as prioritization mechanisms. Contra-*: optimize the mempool size and help in countering the effects of DoS attacks due to spam transactions. We evaluate Contra-* by simulations and analyze their effectiveness under various attack conditions