Authors: Behzad Abdolmaleki and Sebastian Ramacher and Daniel Slamanig
Abstract: Zero-knowledge proofs and in particular succinct non-interactive zero-knowledge proofs (so called zk-SNARKs) are getting increasingly used in real-world applications, with cryptocurrencies being the prime example. Simulation extractability (SE) is a strong security notion of zk-SNARKs which informally ensures non-malleability of proofs. This property is acknowledged as being highly important by leading companies in this field such as Zcash and supported by various attacks against the malleability of cryptographic primitives in the past. Another problematic issue for the practical use of zk-SNARKs is the requirement of a fully trusted setup, as especially for large-scale decentralized applications finding a trusted party that runs the setup is practically impossible. Quite recently, the study of approaches to relax or even remove the trust in the setup procedure, and in particular subversion as well as updatable zk-SNARKs (with latter being the most promising approach), has been initiated and received considerable attention since then. Unfortunately, so far SE-SNARKs with aforementioned properties are only constructed in an ad-hoc manner and no generic techniques are available.