COSigna — Sign documents the server never sees

Everyone signs the same document — and each signer vouches for the one before

The Ring of Mutual Consent

A COSigna ceremony is a ring, not a queue. Each signer signs on top of the one before — and every signature proves two things at once, not one. The document never leaves anyone's machine.

Same document, link by link — before signing, each signer's device checks the document is byte-for-byte the same one the previous signer approved. The exact same bytes travel the whole ring — held by no one, not even the server.

Each signer recognizes the one before — people who already know each other. Each signer sees the previous signer's consent selfie and confirms it's them, so the ring of participants is vouched for as it grows.

Closing the ring proves the whole — everyone was recognized, everyone signed the exact same document, and it never left a single machine. Verifiable offline, by anyone, forever.

How COSigna compares — and what the others make you depend on

Every other tool makes you depend on it. COSigna depends on nothing you don't already control.

How is COSigna simpler?
Simpler for your signers, simpler for you to keep. They open a link, see the document, seal it — no account, no app, no upload. You keep one self-contained proof file instead of a vendor account you must keep alive.

Why is it better — and what does risk-free mean?
Better, because the proof outlasts any vendor — it is yours, and it verifies without us, forever. Risk-free means the trial: no account, no card, no data surrendered, and the test certificate is yours to keep. One ceremony, not a migration — your DocuSign workflows stay where they are.

	COSignaDepends on: a blind server that only ever holds a fingerprint — plus open verification anyone can run.	Cloud e-signatureDocuSign, Adobe Sign, Dropbox Sign, PandaDoc, SignNowDepends on: their servers (which hold your document) + your account	EU QES platformsYousign, Skribble, Scrive, Namirial, Universign, Lex Persona, OodriveDepends on: their QTSP servers + an identity provider	Timestamp-only servicesOpenTimestamps, OriginStamp, BernsteinDepends on: their service to store & return the proof
The document never leaves the signers' machines	✓	✗	✗	✓
Mutual human (face) attestation	✓	✗	~	✗
Permanent independent timestamp (Bitcoin)	✓	✗	✗	✓
Verifiable offline, forever, with no vendor	✓	✗	✗	~
Identity comes from people, not passwords	✓	✗	✗	~
Survives the vendor disappearing — no lock-in	✓	✗	✗	~

For lawyers & notaries

COSigna is a ceremony layer. A qualified professional signing inside the ring with their own QSCD turns the ring into a qualified eIDAS signature on the document.

The ring protocol is protected by European Patent EP3665600B1 and US Patent 11,531,746 (Phileos). View patent → View US patent →

Full technical brief for legal professionals →

How the proof lasts

Proof that outlasts any vendor — verifiable offline, forever.

Trust your COSignees, not the platform — the math makes that enough.

Each sealed ceremony is anchored to Bitcoin via OpenTimestamps — an independent, permanent timestamp that requires no account and no ongoing relationship with COSigna.

The offline verifier is a single HTML file you can save today and run in ten years, with no internet, to verify any COSigna ceremony. No dependency on cosigna.eu — ever.

Verify a ceremony →

For organisations

COSigna fits inside your existing processes. No migration, no vendor lock-in. Run a pilot ceremony today — your signers need no account and no app.

The operating organisation is a witness, never a master — the ceremony belongs to its participants, not to the platform or the institution.

White-label ready — your domain, your colours, your participants. The cryptographic proof is identical; the surface is yours.

Verifiable by anyone, forever — your internal compliance, your external auditors, your counterparties can all verify the ceremony from the certificate file, with no dependency on COSigna.

Full brief for organisations →

What you keep with an account

We keep your proof — never your document or your face. Your Ceremony Certificates stay with you: searchable, re-downloadable, yours.

Sign together. Everyone keeps the proof.

Document Signing, Decentralized.