What is UTS?

Universal Timestamps (UTS) is a decentralized timestamping protocol that enables anyone to create cryptographic, publicly verifiable proofs that data existed at a specific point in time.

The Problem

Consider a common scenario: you write a document, invent a design, or generate a dataset. Later, someone disputes when that data came into existence. How do you prove the data existed at a certain time without relying on a trusted third party?

Traditional approaches — notary stamps, trusted servers, email timestamps — all share a common weakness: they depend on a single entity that must be trusted not to backdate, forge, or lose records. A compromised notary or a deleted email server destroys the proof.

The Analogy: Digital Notarization

Think of UTS as a digital notary backed by a public blockchain:

1. You bring your document (any data) to the notary.
2. The notary doesn’t read your document — it only sees a cryptographic hash (a fixed-size fingerprint).
3. The notary records that hash into a public, append-only ledger that anyone can audit.
4. Later, anyone can verify the timestamp by re-hashing the original data and checking the ledger.

Unlike a physical notary, UTS requires no trust in any single party. The ledger is a blockchain — immutable, publicly verifiable, and decentralized.

Why Blockchain?

Blockchains provide three properties that are ideal for timestamping:

• Immutability — once a transaction is confirmed, it cannot be altered or removed.
• Public verifiability — anyone can independently verify that a hash was recorded at a given block height.
• No trusted third party — the security guarantee comes from the consensus mechanism, not from any single operator.

OpenTimestamps Heritage

UTS extends the OpenTimestamps protocol, which pioneered blockchain-based timestamping on Bitcoin. OpenTimestamps introduced several key ideas:

• A compact binary codec (.ots files) that encodes hash operations as a directed acyclic graph of opcodes.
• Calendar servers that aggregate many timestamp requests and batch them into a single on-chain transaction.
• Merkle tree batching — thousands of timestamps share a single blockchain transaction by constructing a Merkle tree and recording only the root on-chain.

UTS builds on this foundation and extends it to Ethereum via the Ethereum Attestation Service (EAS), using a dual-layer architecture across L2 (Scroll) and L1 (Ethereum mainnet).

Key Insight: Cost Amortization

A single Ethereum transaction costs gas regardless of whether it timestamps one hash or one thousand. UTS exploits this by batching: a calendar server collects many user digests, builds a Merkle tree from them, and records only the 32-byte Merkle root on-chain. Each user receives a Merkle proof that links their specific hash to that on-chain root.

The result: the per-timestamp cost drops by orders of magnitude, making cryptographic timestamping practical for everyday use.

What You’ll Learn

This book walks through the UTS architecture from first principles:

• Chapter 2 gives a high-level system overview and introduces all components.
• Chapter 3 explains the core data structures: Merkle trees, the OTS codec, and the journal.
• Chapter 4 traces the calendar timestamping pipeline end-to-end.
• Chapter 5 covers the L1 anchoring pipeline for cross-chain security.
• Chapter 6 describes the storage architecture.
• Chapter 7 discusses security considerations.
• Appendix A explains the drand beacon injector.