Learn / Overview
Mark Documentation
Mark is a sovereign digital signing protocol and app. Sign documents with a cryptographic signature anyone can verify — without depending on any platform.
What Mark is
Mark is two things: the Mark Signing Protocol (MSP), an open standard for cryptographic document signing with tiered identity assurance, and the Mark app, the reference implementation that makes the protocol accessible on your phone.
Every signature Mark produces is a self-contained proof package — a SignedBundle — that includes everything needed to verify: the cryptographic signature, the key authorization chain, timestamps, and identity pointers. Verification resolves to public blockchains and published cryptography, not to our servers.
The protocol layers
4 layersLayer
What it proves
Required?
0 — Cryptographic proof
Someone who controls key X signed document Y at time T
Always
1 — Identity persistence
The signer has a discoverable, persistent identity
Recommended
2 — Temporal anchoring
Independent proof of when (Bitcoin / RFC 3161)
Optional
3 — Identity assurance
Who the signer is in the real world (trust tiers)
Optional
What Mark replaces
Existing tool
Why it falls short
DocuSign / Adobe Sign
Centralized — platform owns verification; signatures die with the platform
PGP
Strong crypto but terrible UX, no legal binding, no structured trust model
PKI / DigiCert
Capturable by corporate root CAs; certificate expiry kills long-term verification
W3C VCs / DIDs
Over-engineered for document signing; good for credentials, not contracts
Quick links
- How It Works — the signing, sharing, and verification flows
- Trust Tiers — what each tier means and how to upgrade
- Security & Privacy — key storage, data posture, threat model
- Sovereignty Model — hosted vs. self-sovereign
- Legal Standing — ESIGN, eIDAS, international compliance
- YubiKey Guide — hardware key setup and usage
- API Reference — integrate Mark signing
- MSP Specification — the full protocol spec
- FAQ — common questions answered