Explore privacy-preserving approaches to transparency logs in this informative conference talk. Delve into the technical details of append-only logs and their growing prominence in infrastructure, including certificate authorities and Sigstore. Examine the challenges of maintaining log integrity while addressing privacy concerns and right to erasure requests. Compare and contrast techniques for providing immutable, auditable logs while preserving users' rights. Learn about hash functions, Merkle trees, witnessing, monitoring, and various transparency log implementations. Discover guiding principles and strategies for balancing transparency and privacy, such as destructive methods, prevention techniques, and ways to keep log operators accountable. Gain insights into the intersection of transparency logs and privacy laws, equipping yourself with knowledge to navigate this complex landscape.