Biblio

Blockchain-based cryptocurrencies secure a decentralized consensus protocol by incentives. The protocol participants, called miners, generate (mine) a series of blocks, each containing monetary transactions created by system users. As incentive for participation, miners receive newly minted currency and transaction fees paid by transaction creators. Blockchain bandwidth limits lead users to pay increasing fees in order to prioritize their transactions. However, most prior work focused on models where fees are negligible. In a notable exception, Carlsten et al. [17] postulated that if incentives come only from fees then a mining gap would form\textasciitilde— miners would avoid mining when the available fees are insufficient. In this work, we analyze cryptocurrency security in realistic settings, taking into account all elements of expenses and rewards. To study when gaps form, we analyze the system as a game we call the gap game. We analyze the game with a combination of symbolic and numeric analysis tools in a wide range of scenarios. Our analysis confirms Carlsten et al.'s postulate; indeed, we show that gaps form well before fees are the only incentive, and analyze the implications on security. Perhaps surprisingly, we show that different miners choose different gap sizes to optimize their utility, even when their operating costs are identical. Alarmingly, we see that the system incentivizes large miner coalitions, reducing system decentralization. We describe the required conditions to avoid the incentive misalignment, providing guidelines for future cryptocurrency design.

In recent years, cyber security oriented research is paying much close attention on Vehicular Adhoc NETworks (VANETs). However, existing vehicular networks do not meet current security requirements. Typically for dynamic networks, maximal decentralization and rapidly changing topology of moving hosts form a number of security issues associated with ensuring access control of hosts, security policy enforcement, and resistance of the routing methods. To solve these problems generally, the paper reviews SDN (software defined networks) based network security architectures of VANET. The following tasks are solved in our work: composing of network security architectures for SDN-VANET (architecture with the central control and shared security servers, decentralized (zoned) architecture, hierarchical architecture); implementation of these architectures in virtual modeling environment; and experimental study of effectiveness of the suggested architectures. With large-scale vehicular networks, architectures with multiple SDN controllers are most effective. In small networks, the architecture with the central control also significantly outperforms the traditional VANET architecture. For the suggested architectures, three control modes are discussed in the paper: central, distributed and hybrid modes. Unlike common architectures, all of the proposed security architectures allow us to establish a security policy in m2m-networks and increase resistance capabilities of self-organizing networks.