ATL Protocol

Anchored Transparency Log (ATL) is a cryptographic protocol for maintaining a privacy-preserving, verifiable, append-only log of facts and evidence from across the digital and physical domains.

Abstract

Unlike traditional transparency logs that require public disclosure of all entries, ATL employs a Selective Disclosure model. It allows a log operator to prove the existence, integrity, and timestamp of specific entries to a verifier without revealing the contents of other entries in the log.

This architecture decouples the verification of the log’s integrity from the visibility of its contents.

The protocol utilizes Merkle Trees (RFC 6962) , JSON Canonicalization Scheme (RFC 8785) , Ed25519 Signatures (RFC 8032) , SHA-256 (RFC 6234) , and RFC 3161  Time-Stamps with detached Evidence Receipts to enable offline-first verification.

Core Principles

Privacy by Design
Only cryptographic hashes are anchored publicly. Private data stays with the owner.

Mathematical Immutability
Facts are bound together using Merkle Trees. Changing one byte breaks the entire proof chain.

Digital Concrete
Checkpoints are anchored into multiple external trust layers to ensure permanent, decentralized proof of existence.

Offline Verification
Evidence receipts contain everything needed for local, autonomous verification without trusting the log operator.

Architecture