Axolotl: Robust Asynchronous Threshold Schnorr

"Preview Talk" (by team Trout) @ TCPT3, in reply to the NIST Threshold Call

Abstract: In this talk, we will present Axolotl, a multi-party pseudo-random function. Axolotl can be executed by arbitrary thresholds over an asynchronous network where participants solely have peer-to-peer channels with each other. Despite this flexibility, Axolotl is concretely efficient, requiring just a few kibibytes be multicast by each participant at the 128-bit security level.

We then premise a threshold Schnorr signing protocol upon Axolotl. The result is a two-round protocol which does not require a consistent set to participate in each round, nor a consistent view over who participated in the first round, avoiding the overhead (and assumptions) required for agreement. We manage to achieve this result without the use of Fully Homomorphic Encryption or similarly heavy cryptography, instead premising our instantiation on a group of unknown order.

Joint work: Hila Dahari-Garbian, Ariel Nof, Luke Parker.

Suggested readings

• Preview Writeup (PDF): Axolotl: Robust Asynchronous Two-Round Threshold Schnorr over Point-to-Point Channels
• Linearly Homomorphic Encryption from DDH (ia.cr/2015/047)
• Two-Round Threshold ECDSA (Trout) trout-plus-plus (GitHub)