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McFly: Verifiable Encryption to the Future Made Practical.

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posted on 2024-03-20, 10:31 authored by Nico Döttling, Lucjan Hanzlik, Bernardo Magri, Stella Wohnig

Blockchain protocols have revolutionized the way individuals and devices can interact and transact over the internet. More recently, a trend has emerged to harness blockchain technology as a catalyst to enable advanced security features in distributed applications, in particular fairness. However, the tools employed to achieve these security features are either resource wasteful (e.g., time-lock primitives) or only efficient in theory (e.g., witness encryption). We present McFly, a protocol that allows one to efficiently ``encrypt a message to the future'' such that the receiver can decrypt the message almost effortlessly. Towards this goal, we design and implement a novel primitive we call signature-based witness encryption and combine it with a BFT blockchain (or a blockchain finality layer) in such a way that the decryption of the message can be piggybacked on the tasks already performed by the blockchain committee, resulting in almost-for-free decryption. To demonstrate the practicality of the McFly protocol, we implemented our signature-based witness encryption scheme and evaluated it on a standard laptop with Intel i7 @2,3 GHz. For the popular BLS12-381 curve, a 381-bit message and a committee of size 500 the encryption time is 9.8s and decryption is 14.8s. The scheme remains practical for a committee of size 2000 with an encryption time of 58s and decryption time of 218s.


Primary Research Area

  • Algorithmic Foundations and Cryptography


@misc{Döttling:Hanzlik:Magri:Wohnig:2022, title = "McFly: Verifiable Encryption to the Future Made Practical.", author = "Döttling, Nico" AND "Hanzlik, Lucjan" AND "Magri, Bernardo" AND "Wohnig, Stella", year = 2022, month = 4 }

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