**00**

*Nguyen Thoi Minh Quan*

**Abstract: **What is the funniest number in cryptography (Episode 2 )? 0 . The reason is that ∀x, x ∗ 0 = 0, i.e., the equation is always satisfied no matter what x is. We’ll use zero to attack zero-knowledge proof (ZKP). In particular, we’ll discuss a critical issue in a cutting-edge ZKP PLONK C++ implementation which allows an attacker to create a forged proof that all verifiers will accept. We’ll show how theory guides the attack’s direction. In practice, the attack works like a charm and we’ll show how the attack falls through a chain of perfectly aligned software cracks.

In the same codebase, there is an independent critical ECDSA bug where (r, s) = (0, 0) is a valid signature for arbitrary keys and messages, but we won’t discuss it further because it’s a known ECDSA attack vector in the Google Wycheproof project that I worked on a few years ago.

All bugs have been responsibly disclosed through the vendor’s bug bounty program with total reward ~ $15,000 (thank you).

**Category / Keywords: **cryptographic protocols / zero-knowledge proof, ZKP, zero

**Date: **received 15 Dec 2021

**Contact author: **msuntmquan at gmail com

**Available format(s): **PDF | BibTeX Citation

**Version: **20211217:142556 (All versions of this report)

**Short URL: **ia.cr/2021/1638

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