Quantidia
Product engineering on a digital-signature SaaS: embeddable SDKs, authentication and certificate-based signing.
- Client
- Quantidia
- Sector
- SaaS · Digital signature
- Location
- Remote
- Period
- 2025 —
Confidential product — no screenshots. The diagram shows a simplified, generic architecture of this kind of platform.
Context
Quantidia is a digital-signature platform. Since August 2025 I've worked on it as a contract software engineer, on the core product flows and the integrations around them.
Challenge
Signing a document with legal weight is not a form submission. It involves identity, sessions, certificates that may live in the cloud, in an HSM or on a physical token, and a signed PDF that must stay verifiable. And customers want all of it inside their own products.
Approach
- Turn product, security and business requirements into clear, reusable frontend architecture.
- Take part in technical decisions and API definitions — not only implementation.
- Investigate issues across system boundaries: browser, SDK, APIs and local components.
What I built
Core product flows
Interfaces and flows for the platform, built with React, Next.js and TypeScript.
Embeddable web SDK
Experiences that run inside other products, communicating through iframes, postMessage and cross-domain messaging.
Authentication & sessions
Authentication and session flows, including OAuth / OIDC, JWT and one-time codes.
Signing flows
Integrations for PAdES signing and certificate-based workflows across cloud, HSM and token providers.
Local integration
Components for local integration with certificates and tokens, built with Electron.
Technologies
- React
- Next.js
- TypeScript
- Electron
- REST APIs
- OAuth / OIDC
- JWT
- PAdES