In the Bitcoin system, a peer-to-peer electronic currency system, the delay overhead in transaction verification prevents the Bitcoin from gaining increasing popularity nowadays as it makes the system vulnerable to double spend attacks. This paper introduces a proximity-aware extension to the current Bitcoin protocol, named Bitcoin Clustering Based Ping Time protocol (BCBPT). The ultimate purpose of the proposed protocol, that is based on how the clusters are formulated and the nodes define their membership, is to improve the transaction propagation delay in the Bitcoin network. In BCBPT, the proximity of connectivity in the Bitcoin network is increased by grouping Bitcoin nodes based on ping latencies between nodes. We show, through simulations, that the proximity base ping latency defines better clustering structures that optimize the performance of the transaction propagation delay. The reduction of the communication link cost measured by the information propagation time between nodes is mainly considered as a key reason for this improvement. Bitcoin Clustering Based Ping Time protocol is more effective at reducing the transaction propagation delay compared to the existing clustering protocol (LBC) that we proposed in our previous work.

Online voting in the UK generally takes place without verifiability mechanisms, with providers that are trusted to provide ballot privacy and correctness of the result. However, replacing existing systems with verifiable voting systems with brand new algorithms and code presents a business risk to election providers. We present an approach for incremental change: adding a Selenebased verifiability layer to an existing online voting system. Selene is a verifiable e-voting protocol that publishes votes in plaintext alongside tracking numbers that enable voters to confirm that their votes have been captured correctly by the system. This results in a system where even the election authority running the system cannot change the result in an undetectable way. This gives stronger guarantees on the integrity of the election than were previously present. This gives an end-to-end verifiable system we call Verify My Vote (VMV). In addition, we outline how this approach supports further incremental changes towards the deployment of fully trustworthy online voting systems. The paper also describes the use of distributed ledger technology as a component of VMV to manage the verifiability data in a decentralised way for resilience and trust.

The mechanism of peers randomly choosing logical neighbors without any knowledge about underlying physical topology can cause a delay overhead in information propagation which makes the system vulnerable to double spend attacks. This paper introduces a proximity-aware extensions to the current Bitcoin protocol, named Master Node Based Clustering (MNBC). The ultimate purpose of the proposed protocol is to improve the information propagation delay in the Bitcoin network.

Privacy and verifiability are crucial security requirements in e-voting systems and combining them is considered to be a challenge given that they seem to be contradictory. On one hand, privacy means that cast votes cannot be traced to the corresponding voters. On the other hand, linkability of voters and their votes is a requirement of verifiability which has the consequence that a voter is able to check their vote in the election result. These two contradictory features can be addressed by adopting privacy-preserving cryptographic primitives, which at the same time as achieving privacy, achieve verifiability. Many end-to-end schemes that support verifiability and privacy have the need for some voter action. This makes ballot casting more complex for voters. We propose the PVPBC voting system, which is an e-voting system that preserves privacy and verifiability without affecting voter usability. The PVPBC voting system uses an effective and distributed method of authorization, which is based on revocable anonymity, by making use of a permissioned distributed ledger and smart contract. In addition, the underlying PVPBC voting system satisfies election verifiability using the Selene voting scheme. The Selene protocol is a verifiable e-voting protocol. It publishes votes in plaintext accompanied by tracking numbers. This enables voters to confirm that their votes have been captured correctly by the system. Numerical experiments support the claim that PVPBC scales well as a function of the number of voters and candidates. In particular, PVPBC’s authorization time increases linearly as a function of the population size. The average latency associated with accessing the system also increases linearly with the voter population size. The latency incurred when a valid authentication transaction is created and sent on the DLT network is 6.275 ms. Empirical results suggest that the cost in GBP for casting and storing an encrypted ballot alongside a tracker commitment is a linear function of the number of candidates, which is an attractive aspect of PVPBC.

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