One central promise of blockchain systems is to mediate interactions of mutually distrusting parties without the need for a trusted third party.
SmartJudge is our lightweight framework to extend existing two-party protocols such as fair exchange or cross-blockchain trades with a conditional dispute resolution procedure.
The rationale behind SmartJudge is that honest parties can jointly execute a protocol at minimal costs, and simultaneously are fully protected via a conditionally callable verifier smart contract in case of a dispute.
Since the insertion of illicit content into public blockchains can have severe consequences for users, we explore and discuss the design space for preventing this insertion.
Our findings show that firewall-like scanning of Bitcoin transactions poses no viable solution to the problem.
However, while content insertion cannot entirely be prevented by technical means, self-verifying blockchain identifiers make currently simple manipulations hard.
Finally, the introduction of mandatory minimum fees can be used to disincentivize content insertion additionally.
CoinParty is a fully decentralized and thus secure Bitcoin mixing service.
Our work uses threshold cryptography to combine the adavantages of centralized and decentralized mixers: high usability and strong security guarantees.