Passport ZK Circuits Security Assessment - Freedom Tool - Rarimo

1. Introduction

The Rarimo team engaged Halborn to conduct a security assessment on their zero knowledge circuits and the verifier, beginning on 23/02/2024 and ending on 08/03/2024. The security assessment was scoped to the circuits provided to the Halborn team.

2. Assessment Summary

The team at Halborn was provided two weeks for the engagement and assigned a full-time security engineer to verify the security of the zero knowledge circuits and the verifier. The security engineer is a blockchain, smart-contract, and ZK security expert with advanced penetration testing, smart-contract hacking, and deep knowledge of multiple blockchain protocols.

The purpose of this assessment is to achieve the following :

- Ensure that the circuits operate as intended.

- Identify potential security issues within the circuits.

- Ensure that the verifier operate as intended.

- Identify potential security issues within the verifier contracts.

In summary, Halborn identified some security risks that were successfully addressed by the Rarimo team.

3. Test Approach and Methodology

Halborn performed a combination of manual and automated security testing to balance efficiency, timeliness, practicality, and accuracy in regard to the scope of this assessment. While manual testing is recommended to uncover flaws in logic, process, and implementation; automated testing techniques help enhance coverage of the code and can quickly identify items that do not follow the security best practices. The following phases and associated tools were used during the assessment:

• Research into architecture and purpose.

• Manual code review and walkthrough.

• Graphing out functionality and contract logic/connectivity/functions.

• Manual testing by custom scripts.

• Used circomspect, a static analyzer and linter.

• Used Picus, which checks for under-constrained bugs.