Seal your word.
Turn promises, agreements, and payment plans you make with another person into a digital, device-signed agreement receipt. No notary, no passwords, in minutes.
For iOS and Android. No password — your phone number is verified over WhatsApp.
Car sale — 2018 Golf
Ali Yılmaz · Mehmet Kaya
- Price: ₺485,000
- Handover: May 15, keys + registration
- Payment: in full upfront, by bank transfer
Receipt code
SEAL-3F8A2D1C
Audit hash
a4f1…c2b9
From word to seal, in five steps.
It's not complicated. Write down what you agreed, pair up, send, seal. Faster than driving to a notary or hunting for a contract template.
- 01
Pick a template
Tap "New Receipt" and choose a ready-made template: debt/loan, freelance work, sale, appointment/service or contractor. Add a short subject if you like.
- 02
Fill in the details
Answer the template's short questions: what, how much, when. SEAL turns your answers into numbered items, and you can add your own.
- 03
Pair with the other person
When you tap Send, SEAL opens a pairing session: enter your name and tap "Create Session" to get a pairing code. The other person joins with it on their phone, and your receipt goes to them. You can also pair first from the home screen with "New Pairing".
- 04
They review it
The receipt lands in their "Incoming" tab. They can approve it, suggest an edit, or reject it. If they suggest an edit, you can accept it, reject it, or revise it again.
- 05
Seal it
When the person whose turn it is approves the latest version, the receipt is sealed. That approval is signed with the Ed25519 key on their device and added to the audit chain. Either of you can download the PDF at any time.
One app for the agreements you make every day.
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Loans and IOUs
Money lent to a friend, family member or colleague, with the amount and repayment date.
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Freelance and contractor work
Scope, delivery date, fee and acceptance criteria, agreed before the work starts.
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Second-hand sales
The item, its price, how it is delivered and the condition it is sold in.
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Appointments and services
The date, time, fee and place of a service you book or provide.
Good contracts need good math.
You're writing something sensitive. What you write should not slip away, change without a trace, or be impersonated. The cryptography under SEAL exists exactly for that. Not marketing — anyone with a receipt's code can see its signature status and audit-chain records.
Device-based signing
Each device generates its own Ed25519 keypair. The private key stays on your phone — the server only stores your public key and uses it to verify your signatures.
Ed25519 · TweetNaCl / PyNaCl
Tamper-evident audit chain
Every signed action on a receipt is added to an append-only log, each entry chained to the one before it with SHA-256. Removing or altering an entry in the middle is mathematically detectable.
SHA-256 append-only
Passwordless, phone-verified
We store no passwords. Phone verification uses Twilio WhatsApp with a 6-digit OTP. Codes are stored as salted SHA-256 hashes, compared in constant time, and expire in 5 minutes.
WhatsApp OTP · Salted SHA-256
Minimum data
No email, no password, no address. Only your phone (E.164) and the display name you enter when pairing. Phone numbers are masked on the public verification page.
PII minimization
Encrypted in transit and at rest
All connections (app → API, OTP, push) use HTTPS, and the MongoDB Atlas database is encrypted at rest.
TLS 1.3 · Atlas at-rest
Public verifiability
Every receipt has a unique code. Anyone with the code can see its status, content hash, signature status and audit-chain records at getseal.app/verify — no app needed.
Public verifiability
Legal note
SEAL produces strong evidence — a tamper-evident record of device-signed actions, whose status anyone with the receipt code can look up — but it does not replace qualified e-signatures (e.g. Turkish NES, EU eIDAS QES). For high-value or formal transactions like deeds and corporate filings, combine SEAL with a notary or a qualified e-signature.
Frequently asked.
Can I edit a receipt after it has been sealed?
No. Once a receipt is sealed, its content is frozen and no further change is accepted. Edits can only be suggested before sealing. If you later agree on something different, create a new receipt; the original stays on record and can still be verified.
What if the other party doesn't respond?
The receipt stays pending. The app doesn't send reminders for you, but you can remind them yourself. Until it's sealed, you can withdraw it from your Archive with "Delete completely" — it's removed for both of you and its verification link stops working — or simply leave it pending. As long as it isn't sealed, there is no approved record of it in SEAL.
Is it free to use?
Creating a new sealed receipt needs a SEAL Plus subscription, monthly or yearly. The app shows the price in your local currency before you subscribe, and eligible new subscribers get their first 3 months free. Everything else is free, with or without Plus: reading your receipts, reviewing and approving receipts other people send you, exporting a PDF of any sealed receipt you are a party to, and public verification. The other person never needs a subscription.
Add weight to your word.
Available on the App Store and Google Play. Reviewing, approving and verifying receipts is free; creating a new sealed receipt requires SEAL Plus, and eligible new subscribers get their first 3 months free.
getseal.app