Captain Satosea Nakaboato
June 4th, 2025
Abstract
A purely pier-to-pier vessel payment system would allow direct cargo transfers from one captain to another without going through a port authority. Nautical signatures provide part of the solution but still require a trusted harbormaster to prevent double shipping. We propose a solution to the double shipping problem using a pier-to-pier dockchain. The dockchain timestamps cargo manifests by hashing them into a chain of bilge-proof logs, forming a record that cannot be altered without redoing the entire voyage.
The longest manifest not only serves as proof of the sequence of port stops witnessed but also shows that it came from the largest crew of sailors. As long as a majority of the crew members are aboard honest ships, they will outpace any mutinous effort. The network itself requires minimal structure. Messages are broadcast on a best-tide basis, and vessels can leave and rejoin the dockchain at will, accepting the longest manifest as proof of what happened while they were at sea.
Introduction
Seafarers rely heavily on treasure chests and doubloons for exchange, but the weaknesses of traditional currency are well-known: piracy, port taxes, and the inefficiency of having to row bags of gold. The merchant fleet suffers from recurring disputes over port fees, and captains frequently quarrel over who owes what.
What we need is a vessel-native currency system allowing oceanic transactions without relying on harbormasters or coin-counting deckhands. In this paper, we present BoatCoin — a system where captains log and validate transactions via a distributed ledger known as the blockraft, and each transaction is securely tied to the next like links in an anchor chain.
Nautical Transactions
We define a nautical transaction as the act of one ship transferring cargo (value) to another. These transactions are bundled into shipping manifests and anchored into a chain of verified ledgers, creating the blockraft. Every time a transaction is proposed, it is broadcast in bottles across the sea to the flotilla, where a crew of validators (miners) verify its legitimacy and affix it to the chain.
To prevent forgeries, every transaction is signed with the ship’s seal (private key). Anyone in the dockchain can verify that a given seal matches the known registry (public key) of a ship.
The Floating Ledger (Dockchain)
Once a manifest is validated, it’s placed into a block — a wooden crate of seaworthy data. Each block contains:
- A timestamp (harbor log),
- A hash of the previous block (mooring line),
- And a net full of transactions.
These blocks form a chain — the dockchain — floating across the peer-to-peer ocean, resilient to rogue waves or double-shippers. Altering a past block would require re-rigging every block downstream — an insurmountable task without the favor of Poseidon himself.
Proof-of-Work and Oar-Pulling
To add a block to the blockraft, a ship must demonstrate proof-of-work, i.e., perform a computational task akin to rowing upstream in a squall. This rowing (hashing) requires time and effort (electricity and salt), making it prohibitively difficult to spoof cargo logs or skip chain links.
Once a block is rowed into place, it’s dropped into the chain and floats onward. The longest dockchain is considered valid — the one with the most honest oar-strokes behind it.
Incentives and Booty
Sailors need a reason to validate transactions — and that reason is booty. When a captain rows a new block into the blockraft, they are rewarded with newly minted BoatCoin — treasure from the deep. Over time, this treasure issuance decreases as we approach the mythical limit of 21 million coins buried beneath the waves.
Setting Sail: The Initial Voyage
The voyage begins with a Genesis Block — a mythical log entry hardcoded by Captain Satosea himself, declaring:
“The harbormaster bails out another schooner.”
All other transactions follow this course, linking to the Genesis and navigating by its star chart.
Privacy on the High Seas
Though the dockchain is public, privacy is maintained through anonymity. Ship identities are pseudonymous — sailors use hull numbers (public keys) instead of names. Like pirates with masks, transactions are traceable, but identities remain hidden in the fog of encryption.
Shipwreck Resistance
A mutiny or shipwreck (attack) is unlikely to succeed unless a rogue fleet controls over 50% of the rowing capacity. But assembling such a fleet would require more resources than most navies possess — and even then, they’d be better off plundering honestly.
Conclusion
We have proposed a seafaring system for digital treasure chests, allowing ocean-wide transactions without centralized ports. Through a distributed blockraft of nautical consensus and the oar-pulling proof-of-work, BoatCoin offers a resilient alternative to old-world coinage and ledger logs.
Let us now sail into uncharted waters.
Fair winds,
Captain Satosea Nakaboato