_Follow along with this video:_ --- ### Signatures Summarized In a nutshell, this is how signing works: 1. Take a private key + message - The message is generally comprised of: data, function selectors, parameters etc 2. Pass both the private key + message into the [**Elliptic Curve Digital Signature Algorithm**](https://en.wikipedia.org/wiki/Elliptic_Curve_Digital_Signature_Algorithm) (ECDSA) - We don't dive deep into ECDSA, but I recommend you do - outputs `v, r, and s` 3. `v, r, and s` are used to verify someone's signature using the precompile `ecrecover`.

Follow along with this video:

Signatures Summarized

In a nutshell, this is how signing works:

Take a private key + message
- The message is generally comprised of: data, function selectors, parameters etc
Pass both the private key + message into the Elliptic Curve Digital Signature Algorithm (ECDSA)
- We don't dive deep into ECDSA, but I recommend you do
- outputs v, r, and s
v, r, and s are used to verify someone's signature using the precompile ecrecover.

Signatures Summarized

Learn how the ECDSA (elliptic curve digital signature algorithm) is leveraged in transactions to verify signatures.

Smart Contract Security Auditor Smart Contract Security

Course Introduction

Duration: 25min

Section 1: Review

Duration: 1h 18min

Section 2: What is a smart contract audit

Duration: 35min

Section 3: Your First Audit | PasswordStore

Duration: 2h 28min

Section 4: Puppy raffle

Duration: 5h 03min

Section 5: TSwap

Duration: 5h 22min

Section 6: Thunder Loan

Duration: 4h 33min

Section 7: Boss Bridge

Duration: 2h 01min

1. Introduction

Patrick introduces the Boss Bridge protocol and the sorts of concepts that will be covered in this section. Duration: 5min

2. Phase 1: Scoping

Learn about scoping, coverage reports, understanding roles, thorough documentation, code coverage, stateful fuzzing tests, and invariant testing. Duration: 6min

3. Phase 2: Recon

Code Review - Static Analysis Tools & Fixing Issues. Patrick leverages Slither and Aderyn to dive into Boss Bridge. Duration: 2min

Patrick details the 'Hans' approach to security reviews and leveraging Hans' Audit Checklist (available on Solodit). Duration: 4min

The audit begins with assessing the documentation and gaining context of the Boss Bridge protocol! Duration: 2min

6. Boss Bridge Diagram

In this lesson we visualize the transaction flow of Boss Bridge using protocol diagrams. Duration: 6min

A brief run through a fairly standard token contract contained in Boss Bridge. Duration: 2min

Patrick scopes out L1Vault.sol for potential security vulnerabilities. Duration: 4min

Approaching low level code during a protocol audits. Duration: 2min

10. Unsupported Opcodes

Learn about the importance of checking compatibility before deploying contracts across different L2s and chains. Duration: 11min

11. L1BossBridge.sol

ZkSync & Boss Bridge Code Analysis - Reentrancy Guard, Message Utils, Pausable Library. Focuses on adding an emergency stop and preventing re-entrancy attacks. Duration: 3min

Patrick introduces the ERC-191 signed data format and how signatures are used in the EVM. Discusses the ecrecover precompile. Duration: 6min

13. Signatures Summarized

Learn how the ECDSA (elliptic curve digital signature algorithm) is leveraged in transactions to verify signatures. Duration: 1min

We dive into EIP-712 and introduce typed structured data hashing and signing with minimalistic examples. Duration: 4min

15. Case Study: Polygon

We dive into the infamous polygon hack as a case study of bridge exploits. Duration: 9min

16. Signatures Recap

Elliptic Curve Digital Signature Algorithm & Verification Explained. Emphasis on ecrecover, V, R and S values, and on-chain data protection. Duration: 1min

17. Recon Continued

Patrick explains ECDSA signing & verification with OpenZeppelin examples, focuses on signature-related bugs within Boss Bridge. Duration: 6min

18. depositTokenToL2

'depositTokenToL2' Function in Brief. The function locks tokens in a vault, triggers L2 minting. Duration: 2min

19. Exploit: Arbitrary From

With the help of Slither, Patrick identifies and discusses an 'Arbitrary From' vulnerability. Duration: 3min

20. Arbitrary From: PoC

We detail a proof of code for our identified 'arbitrary from' vulnerability. Duration: 4min

21. Recon Continued (again)

Static analysis using Slither identifies potential vulnerabilities, Patrick issues a warning for false positives. Duration: 5min

22. Exploit: Infinite Mint

Highlights the "Infinite Mint" vulnerability in Boss Bridge that allows any user to steal funds if the vault approves the bridge. Duration: 4min

23. Why Are These Not The Same Finding?

Patrick discusses how to identify if similar findings are recognized as unique bugs and how to determine distinct vulnerabilities by considering the root cause. Duration: 2min

24. Recon Continued Again (again)

Dive into the withdraw function and the potential protections versus replay attacks. Duration: 6min

25. Exploit: Signature Replay

Learn about cryptographic verification and blockchain signatures as well as preserving the integrity of signed messages. Duration: 1min

26. Signature Replay: Minimized

Create a Signature Replay Attack using sc-exploits-minimized in Remix! Duration: 2min

27. Signature Replay PoC

We walk through a PoC for signature replay attacks with Patrick. Duration: 7min

28. Signature Replay: Prevention

Learn about nonce-based protection against replay attacks in transaction handling. Duration: 1min

29. Exploit: Low Level Call to Itself

Patrick focuses on identifying and resolving two significant security issues within Boss Bridge. Duration: 2min

30. Exploit: Gas Bomb

Patrick details a gas bomb attack and how gas costs can be manipulated, with test cases. Duration: 1min

Recap vulnerabilities including chain incompatibilities, signature replays, and bridge hacks. Emphasizes the importance of learning through PoCs. Duration: 5min

Patrick details a number of exercises to take to supplement the learnings of this section! Duration: 2min

Section 8: MEV & Governance

Duration: 1h 40min