Finding Safety in Numbers with Secure Allegation Escrows

For fear of retribution, the victim of a crime may be willing to report it only if other victims of the same perpetrator also step forward. Common examples include 1) identifying oneself as the victim of sexual harassment, especially by a person in a position of authority or 2) accusing an influential politician, an authoritarian government, or ones own employer of corruption. To handle such situations, legal literature has proposed the concept of an allegation escrow: a neutral third-party that collects allegations anonymously, matches them against each other, and de-anonymizes allegers only after de-anonymity thresholds (in terms of number of co-allegers), pre-specified by the allegers, are reached. An allegation escrow can be realized as a single trusted third party; however, this party must be trusted to keep the identity of the alleger and content of the allegation private. To address this problem, this paper introduces Secure Allegation Escrows (SAE, pronounced "say"). A SAE is a group of parties with independent interests and motives, acting jointly as an escrow for collecting allegations from individuals, matching the allegations, and de-anonymizing the allegations when designated thresholds are reached. By design, SAEs provide a very strong property: No less than a majority of parties constituting a SAE can de-anonymize or disclose the content of an allegation without a sufficient number of matching allegations (even in collusion with any number of other allegers). Once a sufficient number of matching allegations exist, the join escrow discloses the allegation with the allegers' identities. We describe how SAEs can be constructed using a novel authentication protocol and a novel allegation matching and bucketing algorithm, provide formal proofs of the security of our constructions, and evaluate a prototype implementation, demonstrating feasibility in practice.Comment: To appear in NDSS 2020. New version includes improvements to writing and proof. The protocol is unchange

Insecure by Design: Protocols for Encrypted Phone Calls

It is increasingly clear that existing phone security mechanisms are inadequate and that change is necessary. Instead of protecting phone conversations from eavesdropping, the UK government's proposed voice encryption standard appears to be designed to facilitate undetectable mass surveillance

Contracts Ex Machina

Smart contracts are self-executing digital transactions using decentralized cryptographic mechanisms for enforcement. They were theorized more than twenty years ago, but the recent development of Bitcoin and blockchain technologies has rekindled excitement about their potential among technologists and industry. Startup companies and major enterprises alike are now developing smart contract solutions for an array of markets, purporting to offer a digital bypass around traditional contract law. For legal scholars, smart contracts pose a significant question: Do smart contracts offer a superior solution to the problems that contract law addresses? In this article, we aim to understand both the potential and the limitations of smart contracts. We conclude that smart contracts offer novel possibilities, may significantly alter the commercial world, and will demand new legal responses. But smart contracts will not displace contract law. Understanding why not brings into focus the essential role of contract law as a remedial institution. In this way, smart contracts actually illuminate the role of contract law more than they obviate it

Blockchain-Based Distributed Marketplace

Developments in Blockchain technology have enabled the creation of smart contracts; i.e., self-executing code that is stored and executed on the Blockchain. This has led to the creation of distributed, decentralised applications, along with frameworks for developing and deploying them easily. This paper describes a proof-of-concept system that implements a distributed online marketplace using the Ethereum framework, where buyers and sellers can engage in e-commerce transactions without the need of a large central entity coordinating the process. The performance of the system was measured in terms of cost of use through the concept of ‘gas usage’. It was determined that such costs are significantly less than that of Amazon and eBay for high volume users. The findings generally support the ability to use Ethereum to create a distributed on-chain market, however, there are still areas that require further research and development