API Signing Process
How identification and remote signing work end-to-end
Our signing API is built around three parties — Simplifi (us), the Client (your platform) and the Subject (the end user). The flow has two phases: identification followed by the issuing of a 3-year certificate, followed by OTP-based signatures.
The three parties
Trust service provider — issues certificates and orchestrates signing.
Your platform — integrates our API and owns the user relationship.
The end user being identified and signing the documents.
Phase 1 — Identification & Certificate Issuance
One-time, valid for 3 years
Client redirects
The Client redirects the Subject to Simplifi's secure identification page.
Onboarding & remote ID
We onboard the Subject and perform remote identification (KYC, liveness, document scan).
Webhook callback
Once complete, we call the Client's webhook with the identification data and certificate reference.
Phase 2 — Document Signing
Repeatable, OTP-based, real-time
Sign request
The Client calls our API with the document (or its hash) to be signed by the Subject.
OTP delivery
Simplifi sends an SMS with a one-time code to the Subject's phone.
Subject enters OTP
The Subject types the OTP inside the Client's app — never leaves the Client UI.
Finalize signing
The Client forwards the OTP to our API; we validate it and finalize the signature.
Legend
All API calls are authenticated with your API key over HTTPS. Webhook callbacks are signed so you can verify their authenticity.