A Survey on Consensus Mechanisms and Mining Strategy Management in Blockchain Networks <s> Verification <s> Abstract Protocols for implementing contract signing, confidential disclosures, and certified mail in an electronic mail system are proposed. These transactions are provably impossible without a trusted intermediary. However, they can be implemented with just a small probability of a participant cheating his partner, by use of a beacon emitting random integers. Applications include privacy protection of personal information in data banks, as well as the protection of business transactions. <s> BIB001 </s> A Survey on Consensus Mechanisms and Mining Strategy Management in Blockchain Networks <s> Verification <s> A peer-to-peer crypto-currency design derived from Satoshi Nakamoto’s Bitcoin. Proof-of-stake replaces proof-of-work to provide most of the network security. Under this hybrid design proof-of-work mainly provides initial minting and is largely non-essential in the long run. Security level of the network is not dependent on energy consumption in the long term thus providing an energyefficient and more cost-competitive peer-to-peer crypto-currency. Proof-of-stake is based on coin age and generated by each node via a hashing scheme bearing similarity to Bitcoin’s but over limited search space. Block chain history and transaction settlement are further protected by a centrally broadcasted checkpoint mechanism. <s> BIB002 </s> A Survey on Consensus Mechanisms and Mining Strategy Management in Blockchain Networks <s> Verification <s> We study decentralized cryptocurrency protocols in which the participants do not deplete physical scarce resources. Such protocols commonly rely on Proof of Stake, i.e., on mechanisms that extend voting power to the stakeholders of the system. We offer analysis of existing protocols that have a substantial amount of popularity. We then present our novel pure Proof of Stake protocols, and argue that they help in mitigating problems that the existing protocols exhibit. <s> BIB003 </s> A Survey on Consensus Mechanisms and Mining Strategy Management in Blockchain Networks <s> Verification <s> We propose a new protocol for a cryptocurrency, that builds upon the Bitcoin protocol by combining its Proof of Work component with a Proof of Stake type of system. Our Proof of Activity protocol offers good security against possibly practical attacks on Bitcoin, and has a relatively low penalty in terms of network communication and storage space. <s> BIB004 </s> A Survey on Consensus Mechanisms and Mining Strategy Management in Blockchain Networks <s> Verification <s> An implicit goal of Bitcoin's reward structure is to diffuse network influence over a diverse, decentralized population of individual participants. Indeed, Bitcoin's security claims rely on no single entity wielding a sufficiently large portion of the network's overall computational power. Unfortunately, rather than participating independently, most Bitcoin miners join coalitions called mining pools in which a central pool administrator largely directs the pool's activity, leading to a consolidation of power. Recently, the largest mining pool has accounted for more than half of network's total mining capacity. Relatedly, "hosted mining" service providers offer their clients the benefit of economies-of-scale, tempting them away from independent participation. We argue that the prevalence of mining coalitions is due to a limitation of the Bitcoin proof-of-work puzzle -- specifically, that it affords an effective mechanism for enforcing cooperation in a coalition. We present several definitions and constructions for "nonoutsourceable" puzzles that thwart such enforcement mechanisms, thereby deterring coalitions. We also provide an implementation and benchmark results for our schemes to show they are practical. <s> BIB005 </s> A Survey on Consensus Mechanisms and Mining Strategy Management in Blockchain Networks <s> Verification <s> In the paper, we present designs for multiple blockchain consensus primitives and a novel blockchain system, all based on the use of trusted execution environments (TEEs), such as Intel SGX-enabled CPUs. First, we show how using TEEs for existing proof of work schemes can make mining equitably distributed by preventing the use of ASICs. Next, we extend the design with proof of time and proof of ownership consensus primitives to make mining energy- and time-efficient. Further improving on these designs, we present a blockchain using a proof of luck consensus protocol. Our proof of luck blockchain uses a TEE platform's random number generation to choose a consensus leader, which offers low-latency transaction validation, deterministic confirmation time, negligible energy consumption, and equitably distributed mining. Lastly, we discuss a potential protection against up to a constant number of compromised TEEs. <s> BIB006 </s> A Survey on Consensus Mechanisms and Mining Strategy Management in Blockchain Networks <s> Verification <s> We present “Ouroboros”, the first blockchain protocol based on proof of stake with rigorous security guarantees. We establish security properties for the protocol comparable to those achieved by the bitcoin blockchain protocol. As the protocol provides a “proof of stake” blockchain discipline, it offers qualitative efficiency advantages over blockchains based on proof of physical resources (e.g., proof of work). We also present a novel reward mechanism for incentivizing Proof of Stake protocols and we prove that, given this mechanism, honest behavior is an approximate Nash equilibrium, thus neutralizing attacks such as selfish mining. <s> BIB007 </s> A Survey on Consensus Mechanisms and Mining Strategy Management in Blockchain Networks <s> Verification <s> This column evaluates blockchain’s roles in strengthening security in the Internet of Things (IoT). Key underlying mechanisms related to the blockchain–IoT security nexus are covered. From a security standpoint, the article highlights how blockchain-based solutions could be, in many aspects, superior to the current IoT ecosystem, which relies mainly on centralized cloud servers. Using practical applications and real-world examples, the article argues that blockchain’s decentralized nature is likely to result in a low susceptibility to manipulation and forgery by malicious participants. Special consideration is given to how blockchain-based identity and access management systems can address some of the key challenges associated with IoT security. The column provides a detailed analysis and description of blockchain’s roles in tracking the sources of insecurity in supply chains related to IoT devices. Using blockchain, it is also possible to contain an IoT security breach in a targeted way after it is discovered. The column also discusses and evaluates initiatives of organizations, interorganizational networks, and industries on the frontlines of blockchain. <s> BIB008
In the verification stage, a verifier checks about the proof's correctness, which is determined solely based on the information issued by the prover. With the paradigm of PoX described above, we are now ready to investigate the puzzle design problem for different PoX schemes, which can be seen as modification or extension to the existing PoW-based Nakamoto protocol (see [37] , BIB002 - BIB006 for examples). Since a trusted third party does not exist in a permissionless blockchain network, special caution should be taken in the puzzle design such that the freshness of the puzzle is guaranteed at the execution stage. Namely, the puzzle solution is unpredictable and the proof is non-reusable. Theoretical analyses of blockchain networks, e.g., BIB007 may assume such a property on the condition that the network has access to a universal random sampler (a.k.a., random oracle) or an ideal randomness beacon BIB008 . Nevertheless, due to full decentralization of the permissionless blockchain networks, a caseby-case study for different PoX schemes is usually needed for practical implementation of the random oracle in order to prevent puzzle grinding and leader election manipulation. Apart from the aforementioned properties of non-invertibility, completeness, soundness and freshness, the other requirements for puzzle design in PoX may include but are not limited to the following: • The puzzle should be resistant to the aggregation  or outsourcing BIB005 of the computational resources. BIB008 The concept of random beacon service is first proposed in BIB001 , where a trusted third party periodically emits random integers to the public. • The puzzle-solving process should be eco-friendly BIB003 , BIB002 , BIB004 , BIB006 ,  . • In addition to providing incentive based on resource pricing mechanism, the puzzle-solving process should provide useful services in the meanwhile [37],  .