Electronic signatures · SaaS · by NexuCentri

Sealed

Signed, sealed and verifiable.

Electronic signatures for businesses, in the same space as DocuSign. Every finished document is digitally sealed, timestamped by an independent authority, and comes with a certificate anyone can verify without uploading the file.

  • 11 languages
  • PAdES digital signature
  • 62 automated tests
  • WCAG AA accessible
Demo: a company uploads an agreement, adds a signer and an approver, places fields and sends it; the signer draws their signature, the approver approves, the document is sealed, and the sealed copy is verified as genuine.
Demo with a fictional company. Every person, company and domain is made up.

The problem

A signature is only as good as your ability to prove it later: who signed, when, and that nothing changed since.

The idea

Make the proof part of the document itself, so it stands on its own, in any PDF reader, years from now.

The result

One sealed PDF: every signature, a signing certificate, a digital signature and a trusted timestamp. Any change shows.

What makes it different

Sealed, not just signed

When the last person finishes, Sealed produces the final PDF once and signs it. The signing certificate lists every signer, their identity check, time zone, device and a tamper-evident trail where each step is chained to the one before.

  • PDF digital signature (PAdES) with an RFC 3161 trusted timestamp
  • Bitcoin timestamp proof (OpenTimestamps) that nobody can backdate
  • Verify page: the file is fingerprinted in the browser and never uploaded
  • Validated with an independent PDF signature checker: intact, whole-file coverage
The signing certificate at the end of a sealed PDF: company logo, the Sealed wax seal, document details, signers with their identity check and time zone, and the drawn signature.

Features

Built for senders and signers

For the people signing

  • No account: a private link, a clear consent step, sign on any phone
  • 11 languages, including Arabic right to left; dates in their own time zone
  • Type or draw a signature; dropdowns, choices, ticks and file uploads
  • Identity checks: an access code or a code sent to their phone
  • Decline with a reason, or pass it to the right colleague

For the business sending

  • Upload a PDF, Word file or photo; drag fields into place
  • Signers, approvers and copies, all at once or in order; sign in person
  • Templates and bulk send from a spreadsheet, with automatic reminders
  • Your logo and colour on signing pages, emails and certificates
  • API and signed webhooks to connect other systems
The editor: people with roles on the right, signature, date and name fields placed on the page.
Editor: people, roles and fields
A completed document: people who signed and approved, the proof panel with fingerprints, digital signature and trusted timestamp, and the signing trail.
Completed: proof and signing trail
Templates page with a saved services agreement, its roles, and Use and Bulk send buttons.
Templates and bulk send
Verify page confirming a sealed PDF is genuine and unchanged, with an independent timestamp.
Verify: genuine and unchanged
Phone, in French: the signer is asked for the access code before anything about the document is shown.
Phone: access code (French)
Phone, in French: the signing page with consent, the document and progress bar.
Phone: signing

Engineering

Built right

Tests

62

Unit, API and browser tests on desktop and phone, light and dark, including two people signing at the same moment

Accessibility

0

axe-core violations, including right-to-left and branded signing pages

Security

Strict

Nonce CSP, hashed one-person links, rate limits, SSRF-safe signed webhooks

Worldwide

Any script

Names in Igbo, Polish, Arabic, Chinese and more print perfectly on the sealed PDF

Next.js React TypeScript libSQL / SQLite pdf-lib PDF.js PKI.js (PAdES) HarfBuzz Playwright Vitest Docker

Interested?

See Sealed with your own documents

Sealed is in private preview. Send me a message on LinkedIn for a live demo.

Request a demo on LinkedIn Back to projects