Paper 2021/323

0

Nguyen Thoi Minh Quan

Abstract

What is the funniest number in cryptography? 0. The reason is that for all x, x*0 = 0, i.e., the equation is always satisfied no matter what x is. This article discusses crypto bugs in four BLS signatures’ libraries (ethereum/py ecc, supranational/blst, herumi/bls, sigp/milagro bls) that revolve around 0. Furthermore, we develop ”splitting zero” attacks to show a weakness in the proof-of-possession aggregate signature scheme standardized in BLS RFC draft v4. Eth2 bug bounties program generously awarded $35,000 in total for the reported bugs.

Note: latest version vs 1st version: clarify attack cost, remove proposed fix because proposing fix without proof is scary, add 1 attack scenario at protocol layer, answer 1 FAQ.