Zero - The Funniest Number in Cryptography

Presented at Black Hat USA 2021, Aug. 4, 2021, 10:20 a.m. (40 minutes)

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 talk will explore crypto bugs in four BLS signatures' libraries (ethereum/py ecc, supranational/blst, herumi/bls, sigp/milagro bls) that revolve around 0. Furthermore, we developed "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.

Presenters:

• Quan Thoi Minh Nguyen - Senior Security Engineer,  
  Quan Thoi Minh Nguyen was nominated to the Black Hat Pwnie Award for Best Cryptographic Attack in 2017 (https://pwnies.com/archive/2017/nominations/#crypto) and the Google Technical Infrastructure Award in 2017 for contributions to the Project Wycheproof (https://github.com/google/wycheproof/blob/master/doc/bugs.md).

Links:

• https://www.blackhat.com/us-21/briefings/schedule/#zero---the-funniest-number-in-cryptography-22890
• https://www.blackhat.com/us-21/briefings/schedule/#zero---the-funniest-number-in-cryptography-228901625065256