What Is a Sealed Reference?

You've probably seen the phrase "sealed reference" on this site. It's a concept we coined, and it's central to everything Attestum does. So let's explain it properly.

A sealed reference is a professional reference that has been written by a verified person, cryptographically sealed so it can't be edited or faked, and permanently owned by the person it's about.

That's the short version. Here's how each piece works.

A Real Person, Verified

When someone writes a sealed reference on Attestum, they verify their identity through their work email address. This isn't a username or a social login — it's a direct confirmation that the person writing the reference is who they say they are, at the organisation they claim to work for.

This matters because the biggest weakness of existing reference systems — from LinkedIn recommendations to written letters — is that anyone can claim to be anyone. There's no verification layer. A sealed reference starts with proof of identity.

Written Once, Sealed Permanently

Once the reference is written and submitted, it gets sealed. Sealing means two things happen simultaneously.

First, the content is encrypted in the writer's browser before it ever reaches our servers. Even Attestum can't read the raw content during transit.^[1]

Second, a cryptographic fingerprint of the reference is recorded on the Base blockchain via the Ethereum Attestation Service. This fingerprint is a one-way hash — it proves the reference existed at a specific moment in time with specific content, but it doesn't reveal the content itself.

The practical effect: if anyone changes even one character of the reference after sealing, the fingerprint breaks. The reference is tamper-proof from the moment it's created.

Owned by the Subject, Not a Platform

This is where sealed references diverge most sharply from everything else on the market.

A LinkedIn recommendation belongs to LinkedIn. An Upwork review belongs to Upwork. A verbal reference given over the phone belongs to nobody — it evaporates the moment the call ends.

A sealed reference belongs to the person it's about. They control who sees it, when, and for how long. They can share it via a secure link with any employer, revoke access at any time, and even build a portfolio of multiple sealed references that they share as a collection.

If Attestum disappeared tomorrow, the cryptographic proof would still exist on the blockchain. The reference would still be verifiable.

How Verification Works

When a recruiter or employer receives a shared link to a sealed reference, they see the reference content, the identity of the person who wrote it, their verification level, and the timestamp of when it was sealed.

They can independently verify that the content hasn't been tampered with — the cryptographic fingerprint confirms it matches the original. The entire process takes about ten seconds.

No phone calls. No scheduling. No wondering whether the person on the other end of the line is who they say they are.

Why "Sealed"?

We chose the word deliberately. A seal implies authenticity, authority, and permanence. Think of a notary seal, a wax seal on a letter, a court seal on a document. It means: a real person endorsed this, at a specific moment, and it hasn't been touched since.

That's what a sealed reference is. A professional endorsement with proof attached.

Who Creates Them?

The flow is simple. A professional asks a colleague, manager, or client to write them a sealed reference on Attestum. The writer receives an invitation, verifies their identity, writes the reference, and seals it. The professional then owns that reference and can share it with any employer, instantly.

Writers can also create references proactively — they don't need an invitation. If you want to endorse someone you've worked with, you can do it directly.

Both creating and writing references are free. Attestum only charges when an employer verifies a reference — the people generating and receiving references never pay.

When Would You Use One?

The most obvious use case is job applications. Instead of listing three phone numbers and hoping your former managers pick up, you share a link to a portfolio of sealed references. The recruiter verifies them in seconds.

But sealed references are useful beyond hiring. Freelancers can collect verified client testimonials they actually own. Consultants can build a portable track record. Academics can gather peer endorsements. Anyone whose professional reputation depends on what other people say about them benefits from having that proof sealed and under their control.

The Bigger Picture

Sealed references are the first product on Attestum, but they're part of a broader vision: making professional trust verifiable, portable, and owned by individuals.

The same sealing technology that protects a professional reference also powers document seals — where creators and professionals can prove they authored a piece of content at a specific point in time. Verified reviews and credentials are on the roadmap.

The core idea is always the same: a verified person binds their identity to a piece of content, and that binding is sealed permanently.

That's what "sealed" means. And that's what Attestum does.

Get Your First Sealed Reference — Free →

Sources

1. Attestum uses AES-256-GCM client-side encryption. Content is encrypted in the browser before transmission. See How It Works for technical details. ↩

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