Picture this

Who it is for

A housing coop in Lisbon takes encrypted offers for a flat; the winning offer is revealed only to the coop.

Two ways to own it

What you get

Base$169

$42 deposit to reserve

Listing, encrypted offers, reveal to owner.

You choose: accent color

Customfrom $1,300

Built around you

Reshape it entirely: new features, your flows, your brand end to end, integrations you need. We scope it with you.

Everything in Base
Custom features and design
Priority build

Why it is new

What exists today, and what this does differently

What is new

Sealed bid demos exist on FHE chains; a rent offer product was not found.

Closest things out there

Generic sealed bid auctions.

Checked with web searches in October 2026. A search is not proof that nothing similar exists, and the market moves fast, so we recheck before every build.

What it unlocks

The human in it

Fair offers, no bidding wars in the open.

The Regatta Board

Races it can enter

buildathon · Fhenix · upcoming

Fhenix buildathon / grants

unknown

Official page ↗

Ecosystem program for shipped apps; check current terms.

Their rule on existing code: unknown

What you own

The whole app, not a starter kit.

The complete Sealed Rent app: landlords and housing coops take sealed, encrypted rent offers on Fhenix, compare them without decrypting, and reveal only the winner to the coop, with a paywall, owner console and intake agent built in.

Base price · $169

The user app, complete

Every buyer gets the same finished app. Basic branding and copy changes come through a quick form.

Three step onboardingHome

Shown once: open offers start bidding wars, one sealed offer each, only the winner comes out.

Listing progress and next actionHome

Listed, offers in, revealed and Thursday, with floor, sealed offers and amounts seen.

Listing rulesListing

Floor rent, winning rule and counts only setting, locked into the listing contract before the first offer.

Lottery and member votesListing

A lottery among offers above the floor and member voting on rules. Gated behind Coop.

Sealed offers from the phoneOffers

Each applicant's offer is encrypted on device; open bidding and a snooping bot shown for contrast.

Intake agentOffers

Answers applicant questions and sends reminders, with no decrypt permission. Gated behind Coop.

Close and revealReveal

At close only the winning offer is decrypted for the coop; others hear not selected; receipt shows what is onchain.

Thursday digestThursday

New flats for applicants and how past flats settled, with a save and streak.

Plans and settingsMe

Per listing or monthly pricing from the owner paywall with crypto checkout, gas sponsoring and unlimited listings gate.

Open the full app demo

Add-on

Owner console

Your admin side: revenue, paywall editor, users, rules and the agent log.

Revenue and paywall editorRevenue

Revenue from listings and coops, payouts, incoming USDC, payment methods and live editing of tier names, prices and gates.

Coop approvalsCoops

Approve coops and landlords, decline agencies that want losing offers.

Rules, agent log and roadmapRules

Close time, reminders, sponsored offers, one offer per applicant and counts only; plus the Agent log and priced Roadmap.

Top-up

Growth and referrals

Referral and growth mechanics, switched on when you are ready to grow.

Coop open evenings and referralsGrowth

Run an open evening with a coop federation, see loops and simulate referrals.

The money path, built in

How it earns for you

Applicants never pay. Landlords pay a fee per listing, and coops pay monthly for unlimited listings, the lottery rule, member votes and the intake agent.

ApplicantFreeMake sealed offers and get the Thursday digest

Landlord$15 per listingOne listing contract, sponsored gas for up to 30 offers, winner reveal

Coop$39 a monthUnlimited listings, lottery rule, member voting on rules, and the intake agent

Rent never passes through the app. FHE gas for offers is typically cents and can be sponsored by the landlord.

Prices are yours to set. Illustrative, not a promise of income.

Growth loops, built in

How it spreads

Listing links shared in neighbourhood groups and housing forums
The Thursday digest that brings applicants back
Coops telling coops about a fair rule
Coop open evenings with federations
Coop referrals worth a free month

Roadmap · build the next phase with us

Where it goes next

v1 included

The full sealed letting app

Listing contracts with floor and rule
Encrypted offers from the phone
Encrypted compare and winner reveal
Thursday digest for applicants
Paywall, owner console, intake agent

Included

Verified applicants and deposits

Applicant verification without sharing documents
Deposit held in escrow
Lease signing handoff
Waitlists for coops

Add-on from $500

City housing programmes

Municipal affordable housing lotteries
Priority groups in the lottery
Public audit of draws
Multi language intake

Add-on from $1,200

For investors and grant reviewers

The pitch, ready

Sealed rent offers: nobody sees anyone else's number, and only the winner is revealed to the landlord.

Problem: Good flats get flooded with offers in public chats. Applicants bid each other up, people who cannot keep raising drop out, and everyone's offer stays visible forever.

Solution: A listing contract on Fhenix takes one encrypted offer per applicant, keeps an encrypted maximum or count, and at close grants the landlord permission to decrypt only the winner. Losing offers are never decrypted.

Why now: Fully homomorphic encryption on Fhenix makes encrypted comparisons practical, and rental markets in cities like Lisbon are under intense pressure.

Market: Housing coops, small landlords and later city affordable housing programmes.

The ask: Pilot with three Lisbon housing coops and a municipal housing partner.

Funding is never guaranteed. Check each program's rules.

For hackathons and demo days

Your 2 minute demo

Home: meet Inês and the Graça coop, whose last flat went up 30% in public rounds.
Listing: set a €950 floor and highest offer, pay $15 for the listing in USDC.
Offers: Amara seals her offer; a snooping bot gets ciphertext.
Reveal: close and reveal only the winner to the coop.
Thursday: applicants who lost get new flats and nobody saw their number.
Owner Agent: the agent asked to decrypt everything and was refused.
Owner Revenue and Coops: change the Coop price, approve a coop, decline an agency.
Owner Growth and Roadmap: run a coop open evening, then request verified applicants.

Many hackathons require code written at the event. See the Regatta Boardfor each race's rule.

Make it entirely yours

Custom work from $1,300: coop branding, a municipal lottery setup, lease integrations or extra languages. Scoped on a call.

Custom from $1,300

BLUEPRINT

Why it matters and how it really works

The need

When a good flat comes up, landlords and housing coops get flooded with offers in public chats and portals. Applicants see each other's numbers and bid each other up, people who cannot keep raising drop out, and everyone's offer stays visible forever. Small landlords and coops want fair offers without running an auction in the open.

What exists and what is new

Sealed bid auctions are a known pattern, and sealed bid demos already exist on FHE chains, including Fhenix examples. Our search did not find a product built for rent offers. What is new is the rental product around the mechanic: a floor rent, a choice between highest offer and a lottery at the floor, an optional encrypted count of offers above the floor, and a reveal of only the winner, only to the landlord. The cryptography is not new; the use and the fairness options are.

The data it runs on

A listing contract with its fixed rules (floor, rule, window), one encrypted offer per applicant stored as FHE ciphertext handles, an encrypted comparison result, and a winner reveal sealed to the landlord's key. Applicant names, references and the lease stay with the landlord, off chain.

1.The mission

Let people offer what they can honestly pay for a home, without being pushed into a bidding war or exposing their number to anyone.

2.Why people can't resist it

No public war Applicants offer once and walk away. No refreshing a group chat to see if someone outbid them.

A fair rule Coops can choose a lottery at the floor rent, so the person with the most money does not always win.

Thursday flats A weekly digest of new coop and small landlord listings, each one offer away.

3.How it works for real

Listing: The landlord creates a listing contract on a Fhenix supported chain with the floor rent, selection rule, offer window and what extra info they may learn.

Encrypt on device: The applicant's offer is encrypted in the browser with Fhenix's cofhejs client and submitted as an encrypted integer. One offer per verified applicant.

Compare encrypted: The contract keeps a running encrypted maximum, or an encrypted count of offers at or above the floor, using FHE comparisons. Nothing is decrypted during the window.

Close and reveal: At close, the contract grants the landlord permission to decrypt only the winning offer and winner identity. With the lottery rule, a random pick among eligible offers is made.

Notify: Applicants are told selected or not selected. Losing offers are never decrypted.

Intake agent: An assistant drafts listings, answers questions and sends reminders before close. It has no decrypt permission.

4.Cost per use and pricing

Each encrypted offer and comparison costs FHE gas, which is higher than a normal transaction but typically cents on current Fhenix testnets and early mainnets; real costs depend on the chain at launch. Gas can be sponsored by the landlord. Example: 20 listings a month with 15 offers each, roughly 300 encrypted submissions plus comparisons, is likely tens of dollars in gas, plus a small server for the agent. Treat these as estimates.

Applicant Free

Make sealed offers and get the Thursday digest.

Landlord $15 per listing

One listing contract, sponsored gas for up to 30 offers, winner reveal.

Coop $39 a month

Unlimited listings, lottery rule, member voting on rules, and the intake agent.

5.Growth loop

Every listing link is shared in neighbourhood groups and housing forums. Applicants who lose still keep the digest and come back on Thursdays. Coops talk to other coops, and a fair rule is a story people repeat.

6.Risks and guardrails

Still an auction: Highest sealed offer can still push rent up. Make the lottery rule easy to pick and show its effect.

Sybil offers: One person could submit many offers. Require a light identity check per applicant, kept by the landlord.

Housing law: Some cities limit rent increases or require certain processes. Landlords must check local rules; the app does not give legal advice.

Discrimination: The landlord still chooses who to rent to after the reveal. Keep a record of the rule and the result for fairness.

FHE maturity: Fhenix tooling is young. Keep contracts small, audited, and avoid storing anything that does not need to be onchain.

7.Build order

Listing contract with floor, rule and window
Browser encryption and one offer per applicant
Encrypted max and count above floor
Winner reveal to landlord only
Selected or not selected notices
Thursday digest

8.Where this is going

Now
Sealed rent offers for a single listing, with highest or lottery rules, on Fhenix.
Next
Coop member voting on rules, waiting list priority, and sponsored gas by default.
Later
Sealed offers for shop leases, allotments and student rooms, anywhere a scarce space draws a crowd.
The world it builds
Homes go to people through fair rules they can see, not through who shouts the biggest number in public.

Costs and tools are estimates at the time of writing. General information only, not legal or financial advice.

OWNER PLAYBOOK

Own it, then chart your voyage

Nine routes from one vessel. Tap a port to open its chart.

Why own Sealed Rent

Sealed Rent: Landlords take sealed encrypted rent offers, and nobody sees the others. Using someone else's version means their rules, their brand and their revenue. Owning Sealed Rent means it is deployed under your wallet, carries your name, and every customer, partner and result builds your track record instead of theirs.