V2 - CPS & Gateway - SilentSwap

1. Introduction

This security assessment was commissioned by SilentSwap, a privacy-focused, non-custodial cross-chain aggregator built on the Secret Network. Conducted by Halborn’s experienced security team, the review focused on the on-chain components in the silentswap-v2-cps and silentswap-v2-gateway repositories. The assessment covered all functionalities within both CPS and Gateway contracts from October 20, 2025 to October 24, 2025. As a non-custodial protocol, SilentSwap never takes possession of user funds, users retain full control of their assets throughout every interaction. The primary objective of this engagement was to identify potential vulnerabilities, verify module reliability, and enhance the overall security posture.

2. Assessment Summary

The team at Halborn assigned a full-time security engineer to verify the security of the smart contracts. The security engineer is a blockchain and smart-contract security expert with advanced penetration testing, smart-contract hacking, and deep knowledge of multiple blockchain protocols.

The purpose of this assessment is to:

• Ensure that smart contract functions operate as intended

• Identify potential security issues with the smart contract

In summary, Halborn identified some improvements to reduce the likelihood and impact of risks. The SilentSwap team remediated the major issues identified. The remaining informational findings have been acknowledged by the team. The main recommendations were the following:

• Fix arguments order when invoking the sign_ecdsa_keccak_256 function.

• Use compressed keys for all Cosmos/Secret semantics (address & Permit).

• Implement a grace period in order to give the notary/claimer a buffer to land claims after expiry, or proof-commit mechanism to reduce operational risk of race conditions.

• Bind the recipient and execution context in the signature.

3. Test Approach and Methodology

An unwaveringly thorough multi-phase strategy was employed for this assessment. The process comprised the following major phases:

• Scoping and threat modeling, including architectural review to identify systemic risk areas.

• Manual line-by-line review of the smart contract source across all identified repositories.

• Automated tooling and static/dynamic analysis to ensure full path coverage and surfacing of subtle runtime vulnerabilities.

• Custom on-chain test case development and execution against all critical user, protocol, and edge-case flows, mapped against real-world threat models for DeFi, cross-chain, and privacy-centric systems.

• Continuous cross-validation of findings among specialists to eliminate blind spots and false negatives.

Manual and automated review phases were balanced for maximum coverage: static analysis flagged issues rapidly, while targeted manual work validated logic, business invariants, and protocol integrations. Major frameworks and off-the-shelf industry toolkits were leveraged, supplemented by custom tests to validate crucial behaviors under adversarial conditions.

4. Confirmation of Non-Custodial Architecture

At the request of SilentSwap, we were tasked with determining whether the platform operates as a non-custodial system. Upon completion of our review, our determination is that SilentSwap’s architecture is non-custodial.

5. Assessment Scope Clarification

The findings documented in this report for the CPS codebase are based on the source code repository provided at the time of the security assessment. Following the conclusion of the assessment, the SilentSwap team shared a new repository containing an updated version of the codebase with fixes applied to the major reported issues. The originally assessed repository is no longer in active use.