Notaries have been the gatekeepers of legal truth for centuries. Walk into any bank, law office, or UPS Store, present your documents, pay $5 to $25, and receive a stamped, sealed certification that you signed something on a certain date before a certain witness. The model is ancient, trusted, and per-document. Every signature costs money, every document requires presence, and every record depends on the notary maintaining their journal.

In 2016, Bitcoin Core developer Peter Todd launched a project that would invert this economic model entirely. OpenTimestamps (OTS) promised something audacious: cryptographic proof-of-existence, forever verifiable against the Bitcoin blockchain, at zero cost to the user — with no account, no API key, and no registration required. Six years later, the system processes thousands of timestamp proofs daily, sustained by donations totaling roughly $35 per week.

How does an economic model this counter-intuitive actually work? Who bears the cost? And what does it tell us about the future of digital public infrastructure?

The OpenTimestamps Economic Architecture

At its core, OpenTimestamps operates on a simple principle: Merkle tree aggregation. Rather than writing each timestamp to the Bitcoin blockchain individually — which would cost ~$0.16-$0.25 per proof at current fee rates — OTS batches thousands of proofs into a single Bitcoin transaction.

The process works in four steps:

1. User submits a file hash to a public calendar server (no account, no payment).
2. The calendar server collects hashes from all users over approximately 1.5 hours.
3. A Merkle tree is constructed from all pending hashes; only the single Merkle root is written to the Bitcoin blockchain via an OP_RETURN output.
4. Each user receives a .ots proof file (~2-10 KB) containing their Merkle proof path, allowing independent verification against Bitcoin block headers — forever.

“OpenTimestamps scales indefinitely, allowing timestamps to be created for free by combining an unlimited number of timestamps into one Bitcoin transaction.” — Peter Todd, OpenTimestamps Announcement, September 15, 2016

Live Economics: The Two Public Calendars

OpenTimestamps currently maintains two public calendar servers — named Alice and Bob — that serve as the public anchoring infrastructure. Their live status pages expose real-time operational data. Here is what they show at any given moment:

At current Bitcoin prices, the combined weekly operating cost is approximately $35 USD — roughly the equivalent of two traditional notarizations. Yet this $35 anchors several thousand proofs, yielding an effective cost per timestamp of approximately $0.00003, or roughly 1/500,000th the cost of a single notary signature.

The Donation Model

How do the calendars sustain themselves? Both Alice and Bob display donation addresses for Bitcoin (on-chain) and the Lightning Network. Their wallet balances — 122,125 sats on Alice ($77) and 34,055 sats on Bob ($21) — indicate a steady trickle of small donations that cover the modest operational costs.

This is not a venture-funded startup. It is digital public infrastructure, maintained by donations and operated at cost. There are no subscription tiers, no premium plans, no API rate limits. The economic model is deliberately minimalist — intentionally aligned with the ethos of a permissionless, censorship-resistant timestamping layer.

The Paradigm Shift: From Pay-Per-Document to Pay-Never

To grasp the magnitude of this economic shift, compare the two models directly:

The most radical column is the last one. A .ots proof file, once created, is a self-contained cryptographic artifact. Verifying it requires only three things:

1. The original file
2. The .ots proof file (~2-10 KB)
3. Any Bitcoin block header (from any pruned or full node)

No calendar server. No ongoing payments. No subscription. If Alice and Bob’s servers disappear tomorrow, every timestamp proof they ever created remains permanently verifiable. The proof anchors to Bitcoin blocks — not to any centralized service.

Why This Matters: Timestamps as Public Goods

Economists define a public good as something that is non-excludable (cannot prevent people from using it) and non-rivalrous (one person’s use does not diminish another’s). Clean air, national defense, and GPS signals are classic examples.

OpenTimestamps approaches this definition with remarkable fidelity:

• Non-excludable: No account, no API key, no payment. Anyone with an internet connection can submit a hash and receive a proof.
• Non-rivalrous: One person timestamping a file does not reduce the capacity for others to do the same — Merkle aggregation means marginal cost trends toward zero as volume increases.

The operators bear a small but real cost (~$35/week), while the benefits are dispersed globally. This is the classic public goods funding problem — and the donation model represents a decentralized solution to it.

The contrast with traditional timestamp infrastructure is stark. GPS — another public good — costs the US government approximately $2 million per day to operate, funded through taxation. The European Union’s EBSI (European Blockchain Services Infrastructure) is building timestamp-based digital credential verification across 27 member states with public funding. Meanwhile, OpenTimestamps provides a globally accessible, cryptographically equivalent service for roughly $1,800 per year in voluntary donations.

The Ethereum Counterpoint: Why Economics Shapes Infrastructure

Not all blockchains are equally suited for timestamp anchoring. Ethereum’s economic model — where every byte of calldata carries a gas cost — makes per-document timestamping substantially more expensive. A single timestamp stored as Ethereum calldata costs approximately $5-$50 (at average gas prices), compared to fractions of a cent on Bitcoin via OTS aggregation.

This is not a technical limitation but an economic one. Ethereum’s high-throughput, general-purpose design makes every state change expensive. Bitcoin’s UTXO model and deliberate simplicity make it an ideal anchor — minimal, stable, and designed for long-term immutability.

The economic consequence is structural: timestamp infrastructure naturally gravitates toward the chain with the lowest marginal anchoring cost. OpenTimestamps chose Bitcoin for this reason, and the choice has proven prescient. No widely-adopted equivalent has emerged on any other chain.

What the Live Data Reveals

Examining the live calendar servers reveals a system operating with remarkable efficiency:

• Transaction cadence: Both calendars anchor approximately every 1.5 hours, creating a steady ~33 daily anchor points on the Bitcoin blockchain.
• Fee optimization: Calendar operators use low fee rates (0.70–3.49 sat/vB), accepting longer confirmation times because timestamp proofs do not require instant finality — a proof is valid once the transaction confirms, whether it takes 10 minutes or 10 hours.
• Self-sustaining rhythm: The donation inflow (~$35/week) is calibrated to operational outflow. There is no surplus extraction — every satoshi spent on fees is a satoshi not extracted as profit.

This is public infrastructure operating at its economic minimum: proof-of-work financialized not as profit, but as a cost-recovery mechanism for providing a global public good.

The Unanswered Questions

For all its elegance, the OTS economic model raises challenging long-term questions:

1. What happens if Bitcoin transaction fees rise dramatically? If BTC fees reach $50+ per transaction (as during the 2017 and 2021 bull markets), the weekly operational cost could spike from $35 to $1,650+. The donation model would need to scale proportionally — or calendar operators would need to batch even more aggressively.

2. Who bears the cost if donations dry up? The two public calendars are maintained by volunteers. If donations falter, the system could lose its public anchoring infrastructure — though existing proofs would remain valid, and anyone could run their own calendar.

3. Is “free” sustainable? Free public goods have a history of being undervalued and underfunded (see: open-source software maintenance, Wikipedia donation drives). OTS may face the same challenge over time.

These questions are not criticisms but acknowledgments that OTS is charting new territory — building public digital infrastructure on a voluntary funding model, without institutional backing, corporate sponsorship, or government subsidy.

Conclusion: The Quiet Revolution

OpenTimestamps is the kind of infrastructure that transforms the world without making headlines. It does not have a token. It does not have a whitepaper promising disruption. It does not even have a funding round. What it has is a working, self-sustaining protocol that has been anchoring cryptographic proofs to Bitcoin for six years — at roughly $1,800 per year in total operational costs.

The economic lesson is profound: blockchain timestamps invert the cost structure of traditional proof-of-existence from pay-per-document to pay-never, while maintaining stronger cryptographic guarantees than any notary seal. The user pays nothing. The operator pays a trivial amount. The proof lasts forever.

In an era of deepfakes, AI-generated content, and escalating epistemic uncertainty, the ability to cryptographically prove that a specific digital file existed at a specific moment in time — at essentially zero marginal cost — may prove to be one of the most important public goods of the 21st century.

— Encryption Archive · StampD.org