# Certificate Transparency with Privacy

## TL;DR

This paper presents privacy-preserving mechanisms for Certificate Transparency logs, allowing browser audits without compromising user privacy and extending support to non-public subdomains, enhancing CT's practicality.

## Contribution

It introduces practical solutions for privacy-preserving CT log auditing and support for non-public subdomains, addressing key privacy challenges in CT deployment.

## Key findings

- Developed a privacy-preserving CT log auditing mechanism
- Extended CT to support non-public subdomains
- Demonstrated the practicality of the proposed solutions

## Abstract

Certificate transparency (CT) is an elegant mechanism designed to detect when a certificate authority (CA) has issued a certificate incorrectly. Many CAs now support CT and it is being actively deployed in browsers. However, a number of privacy-related challenges remain. In this paper we propose practical solutions to two issues. First, we develop a mechanism that enables web browsers to audit a CT log without violating user privacy. Second, we extend CT to support non-public subdomains.