cashr: RSVPs without a guest list
Host an event whose attendee list can never leak. Set a deposit and a capacity; no account needed.
▶ Play: create an eventFor groups that can’t afford a leaked list
The guest list is the liability. So we don’t keep one.
RSVP with a refundable deposit
Attendees scan one QR code with any Zcash wallet. The deposit is shielded: nobody can see who paid, including the organiser.
Show a ticket at the door
The ticket is a random secret made on the attendee's phone. The door checks its hash against a list of hashes, and never learns a name.
Get the deposit back
Everyone who came is refunded automatically, to an address only they know. No-show deposits go to the group's fund.
If the organiser’s laptop is seized
There is nothing on it to find.
Every RSVP tool keeps a database of people. Breaches, subpoenas and stolen devices turn it into a target list. cashr stores no names, emails or phone numbers: only random ticket hashes, one-time refund addresses and payment records, and it deletes them when the organiser purges the event.
That works because of Zcash’s shielded pool: a deposit can come from someone unknown, and a refund can go back to them, with nothing on the public chain linking either to a person.
Read the threat model| A seized server reveals | Typical RSVP tool | cashr |
|---|---|---|
| Names | Every attendee | None |
| Emails / phone numbers | Every attendee | None |
| Wallet or card details | Every attendee | None |
| Who paid | Yes | Hidden by the shielded pool |
| Who showed up | Check-in list with timestamps | Which anonymous tickets came, no times; only a count after the purge |
| After the event | Kept forever | Deleted with one click |
Running something sensitive this week?
Create an event in a minute. No account, no email, no name: not for you, and not for your attendees.