Process
Rent your neighbor's bike. Bring it back.
Four steps. The homepage gives them as a single tight sentence each. This page is the long version, for anyone who would like to read the mechanism before trying it.
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Step one
An owner lists a bike.
Somewhere in Kreis 4 there is a bike against a wall, a person who owns it, and a number of hours in the day during which it is not being ridden. The owner takes a few photographs, writes a sentence or two, sets a price for the hour or the day, and chooses a refundable deposit. The deposit is the only number that does real work; it should be the cost of the worst thing that could plausibly happen to the bike. A good lock, a good tire, a few small parts.
What happens on the chain
Listing writes a small record on the public chain: who the owner is, what the asset is, the price and deposit. The record is not the bike — the bike stays where it always was — but anyone, including a renter who has never met the owner, can verify that the offer exists and has not been edited.
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Step two
A renter agrees.
A renter finds the bike, reads the terms, and agrees. The fee and the deposit move together into a place neither party controls. The owner cannot withdraw them. DaiZen cannot withdraw them. They sit, visibly, until the rental is over. The renter has a window of time within which the bike is theirs to use. The owner has a guarantee that, whatever happens, the deposit is real.
What happens on the chain
What we call "a place neither party controls" is a small contract on the chain. It has been written once, audited once, and now does the same thing forever: hold the funds, release them when the conditions are met. There is no admin button. There is no key the company holds. If we leave, the contract keeps doing its work.
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Step three
The renter rides.
The lock on the bike accepts a one-time key, valid for the agreed window and nothing else. The renter rides to work, to the lake, to a friend's apartment, home. If the rental was for the day, the key works for the day. If it was for the hour, the key stops working when the hour is up. The bike comes back to the same rack, or to wherever the owner asked.
What happens on the chain
The key is a signed message the lock recognises. The signature is bound to the rental window — outside that window, the lock will not turn. If the lock is offline (a basement, a tunnel), the renter's phone holds a cached version and the lock catches up later. The on-chain record is the deciding witness if anything is contested.
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Step four
The bike comes back.
If everything is as agreed, the deposit returns to the renter and the fee moves to the owner — automatically, in the same minute. No invoice, no waiting, no support ticket. If something is not as agreed — a flat tire, a missing bell, a frame the renter says was already scratched and the owner says was not — the rental does not close. It goes, instead, to the bike guild. We come back to that in the next section.
What happens on the chain
Settlement is the contract's last act. It writes an on-chain receipt that says: this rental happened, this is what was paid, this is what was returned. The receipt is permanent. The renter can show it as proof of return. The owner can show it as proof of payment. The next renter, two years from now, can read it as one more data point about a bike that has rented well.
When something goes wrong.
Most rentals close in step four. A small number do not — a chain comes off, a fender bends, a renter is late, an owner disagrees about what counted as fair use. The deposit holds in place. The rental does not settle. The two of you can talk; most disagreements end there. If they do not, the rental moves to the guild — a small group of bike people who decide what counts and what does not. Their decision is on-chain, and so is the reasoning. Nothing about it is opaque, and nothing about it is decided by us.
The guild has its own page. Read about the guild →