ZKP学习笔记

ZK-Learning MOOC课程笔记

Lecture 15: Secure ZK Circuits via Formal Methods (Guest Lecturer: Yu Feng (UCSB & Veridise))

• Motivation
  

  • Bugs in blockchain software are extremely dangers and costly.
  • Smart Contract Bugs, Blockchain Protocol Bugs, ZK Bugs…
  • Formal methods can eradicate these bugs

15.1 Formal Methods in a Nutshell

• What is Formal Method

  • Set of mathematically rigorous techniques for finding bugs and constructing proofs about software
    

• Fundamentals of Static Analysis

  • Abstract Inter-pretation

    • Cannot reason about the exact program behavior due to undecidability
    • Obtain a conservative over-approximation and this can be enough to prove program correctness
    • Abstract interpretation is a framework for computing overapproximations of program states

  • Example
    

    • Program is safe: the intersection between the green and red regions is empty
      

  • Concrete Interpretation is Easy
    

• Abstract Interpretation
  

• Example: Detect Reentrancy via Abstract Interpretation
  

  • External call followed by a storage update

• Other vulnerabilities

  • Integer Overflow
  • Transaction Order Dependence
  • Flashloan Attack

• Abstract Interpretation Tools in Web3

  • Slither (TrailOfBits)
  • Sailfish (Bose et al, Oakland’ 22)
  • Vanguard (Veridise)
  • Securify (CCS '19)

• Shortcomings
  

• Static Analysis via Formal Verification
  

  • Overview
    

  • Example
    

  • When Formal Verification Fails
    

  • Bounded and Unbounded Verification
    

  • Different Flavors of Static Analysis