Introduction to Chaindoc

Chaindoc is an e-signature and document management platform for developers. Every signature is a PAdES cryptographic signature embedded in the PDF, and every signed document's hash is anchored to the blockchain. two independent integrity layers you can verify from any PDF reader and from a public portal.

What is Chaindoc?

Chaindoc handles three things: documents, signatures, and team collaboration. Every published document gets anchored to the blockchain, which means tampering is detectable years after the fact. That's the part most signing tools skip. Learn more in the eIDAS Regulation (EU) No 910/2014.

It's built for developers who want to embed signing into their own apps, but it also works out of the box through the web interface. You don't need to write code to send your first signature request. Learn more in the ESIGN Act of 2000 (15 U.S.C. § 7001).

Two integrity layers

PAdES signature: a cryptographic signature embedded inside the PDF, tied to a per-user ECDSA certificate. Validates in any PDF reader (Adobe, Preview, Foxit). Qualifies as an Advanced Electronic Signature under Article 26 of eIDAS.

Blockchain anchor: a hash of the signed document is written to the blockchain so anyone can re-hash the file years later and confirm it hasn't changed. independent of the PDF layer.

What you can do with Chaindoc

Electronic signatures

Chaindoc produces PAdES Advanced Electronic Signatures that are legally recognised under eIDAS, the ESIGN Act, UETA, and similar frameworks. The signing flow uses email-OTP authentication. signers verify their email, review the document, and sign. Multi-party signing is parallel: every signer receives an invitation at the same time and completes their signature independently.

Blockchain verification

When a document is published, its hash is written on-chain automatically (SKALE Calypso today). No configuration required. You get a transaction hash and chain ID back in the verification record. integrators can re-check integrity programmatically, or anyone can upload the PDF to the public verification portal. Learn more in the UETA.

Document management

Version control with a full audit trail for every change
Actually, pDF, Office files, images, and video uploads (up to 250 MB per file through the current upload API)
Access control: private, public, team, or restricted
Metadata, hashtags, and search to find things fast

If you're coming from shared-drive storage, the biggest difference is the audit trail. Every view, edit, and signature gets logged. See the document management guide for details.

Developer tools

Chaindoc exposes a REST API and two TypeScript SDKs: a Server SDK for Node.js backends, and a framework-agnostic Embed SDK that drops a signing iframe into any web app. works with React, Vue, Angular, Svelte, or plain JS without framework-specific packages.

Full REST API under /api/v1/* with sk_/pk_ key auth and rate limits
Server SDK for Node.js. documents, signatures, contracts, invoices, templates, webhook verification
Embed SDK for browser. drop-in signing flow with modal or inline mode
Webhooks. 17 event types for real-time notifications, HMAC-SHA256 signed
Actually, separate staging environment for development (set environment: 'staging' on the SDK)

Team collaboration

Invite team members into a shared workspace with role-based access. Three default roles ship out of the box. Owner (full control including billing), Admin (manage members and documents), and User (documents and collaboration). The workspace owner can rename existing roles, change their permission sets, and add custom roles as needed. See the team management page for role details.

For teams that need identity verification, Chaindoc integrates with Sumsub for KYC checks.

How the signing flow works

Actually, the typical flow from upload to signed document takes six steps. Most of it is automated once the request is set up.

1
Upload your documentUpload a PDF, Office file, or image through the web interface or via the API. The file is stored and assigned a unique ID.
2
Create a signature requestAdd recipients, optionally place signature fields on specific pages, set a deadline, write a message. In the UI this takes about 30 seconds.
3
Signers get notifiedActually, every recipient receives an email with a secure signing link. If you're using the Embed SDK, the signing UI opens inside your own app instead.
4
Signers review and signEach signer enters an email OTP, reviews the document, and applies their signature (type, draw, upload, or reuse a saved one). The backend produces a PAdES-signed PDF with the signer's ECDSA certificate.
5
Blockchain anchoringOnce all parties sign, the document hash is written on-chain automatically. The transaction hash and chain ID become part of the verification record.
6
Everyone gets the signed copyAll parties receive the PAdES-signed PDF along with a certificate of completion. You can verify authenticity anytime. from any PDF reader, or via chaindoc.io/pdf-verify.

Common use cases

Chaindoc works across industries, but here's where teams get the most value:

Legal and compliance: contracts, NDAs, employment agreements. The blockchain audit trail satisfies most regulatory requirements without extra paperwork.
Real estate: property agreements and lease contracts where you need an immutable record that holds up in disputes.
Financial services: loan agreements, investment documents, compliance forms.
Healthcare: patient consent forms and medical records.
Enterprise: internal approvals, HR documents, vendor agreements. Teams processing hundreds of contracts a month save the most time by automating with the API.

Architecture overview

You don't need to understand the full stack to use the API, but it helps to know what's running under the hood:

Web app built on Next.js + React
Actually, node.js (NestJS + Fastify) REST API with key-based auth, rate limiting, and versioning
PostgreSQL for structured data, S3 for file storage
EU DSS-backed PAdES signing pipeline with per-user ECDSA certificates
Smart contracts on SKALE Calypso for document verification anchoring
Redis + BullMQ for background jobs (webhook delivery, blockchain anchoring, reminders)
CloudFront CDN for document delivery

Security and compliance

Security is baked into how documents are stored, transmitted, and verified.

What's covered

AES-256 encryption for data at rest and TLS for data in transit

Passwordless authentication. Chaindoc users sign in with email-based one-time codes, no stored passwords

PAdES signatures with per-user ECDSA certificates issued by Chaindoc's CA

Optional IP allowlists on API keys (CIDR ranges, individual IPs, wildcards)

Compliance with GDPR, eIDAS (Article 26 AES), the ESIGN Act, and UETA

Regular third-party security audits and penetration testing

For production hardening (key rotation, webhook HMAC verification, monitoring) see the security best practices guide.

Where to go next

Pick the path that matches what you're trying to do:

Quick Start. send your first document for signing in under 10 minutes
Installation. set up the SDKs in your dev environment
API documentation. full REST API reference with examples
SDKs. Node.js Server SDK and browser Embed SDK

First time here?

Start with the Quick Start guide. It walks you through the full signing flow in about 10 minutes, no SDK setup required. If you already know what you're building, jump straight to the API docs.

Frequently asked questions

Quick answers to the questions developers ask most often.

What is Chaindoc?

Chaindoc is a document management and e-signature platform built on blockchain technology. It helps businesses create, sign, store, and verify documents with tamper-evident integrity.

Is Chaindoc compliant with eIDAS and the ESIGN Act?

Yes. Chaindoc signatures are PAdES-BES Advanced Electronic Signatures under eIDAS Article 26 (AES tier) and meet ESIGN Act and UETA requirements in the US. Signatures include timestamped audit trails and cryptographic proof of integrity, with an additional blockchain-anchored hash for independent verification.

Who should use Chaindoc?

Chaindoc fits teams that need legally binding signatures, transparent audit trails, and document workflows. Typical users include legal teams, HR departments, real estate agencies, and SaaS companies.

How does blockchain anchoring work?

Every signed document receives a cryptographic hash that's anchored to a public blockchain. This creates an immutable record that proves the document existed in its signed form at a specific point in time.

Can I try Chaindoc without a contract?

Actually, yes. You can create an account and explore the platform. Some features, such as API access and advanced security controls, require a paid plan.