The evolution of trust.
An electronic signature and contract platform that does not ask you to trust it — it proves. Every document is cryptographically sealed, with the full trail of what happened attached and verifiable by anyone, even without access to the platform.
ICP-Brasil Qualified Signatures · PAdES sealing · Immutable audit trail · LGPD compliant
Legal validity built, not promised
Qualified Signature with an ICP-Brasil certificate, or Advanced Signature with rigorous evidence collection — under Brazilian MP 2.200-2/2001 and Law 14.063/2020.
Proof that outlives the platform
The final PDF carries a digitally signed manifest and audit trail. An auditor verifies integrity offline, without depending on us.
Built for companies
Multi-tenant with database-level isolation, roles and departments, your client's brand on the signing page, and integration with your ERP.
The problem with nearly every signature platform
They ask for trust. We deliver verification.
In most tools, the audit trail is just a table inside the vendor's database. If someone with administrative access edits a row — a timestamp, an IP address, a message — there is no practical way to notice. The proof rests entirely on the integrity of whoever holds the database.
JustSign inverts that. Every event in the document's life enters a chained cryptographic ledger: altering any record breaks verification for all subsequent ones, and the break is detectable even by the system owner. That chain is then printed into the document and protected by the platform's digital signature.
The practical result: in an audit or a dispute, you don't argue that the record is trustworthy. You demonstrate it.
How it works
From uploading the contract to the sealed copy, in four steps.
Upload the document
Add one or more PDFs. The platform computes each file's SHA-256 hash at upload — that fingerprint later proves nothing was swapped along the way.
Define who signs, and where
Add signers, choose each signature type, require witnesses per party when needed, and place signature fields by clicking directly on the document.
Negotiate and sign
If the deal is still under discussion, the Secure Deal Room keeps the chat beside the document — immutable and attached to the final file. Signing happens by digital certificate or on the phone, capturing the handwritten stroke.
Receive the sealed copy
When the last signer completes, the platform assembles the final document with manifest and audit trail, seals it with PAdES using the company certificate, and emails the secure link to everyone involved.
Two modes, in the same document
Not every signer has a digital certificate — and not every contract needs one. Both coexist in the same envelope.
Qualified Signature
The legal gold standard, with an ICP-Brasil certificate.
- Mutual authentication (mTLS) straight from the signer's token or certificate
- Extraction and cross-check of the holder's tax ID, including the legal representative
- Automatic verification of corporate signing powers via the SERPRO gateway
- Presumption of authenticity under MP 2.200-2/2001
Advanced Signature
For signers without a certificate, with validity built from evidence.
- Stroke capture on the phone: scan the QR code and sign with your finger, no install
- The desktop screen updates instantly, with no page reload
- Single-use link, valid for 5 minutes, invalidated the moment it is used
- IP, device, geolocation, timestamp and stroke biometrics recorded
What only JustSign does
Features born from the same obsession: turning every step into evidence.
Secure Deal Room
Negotiation chat beside the document, append-only and cryptographically chained. The negotiation history becomes an attachment to the signed contract — what was agreed in writing is neither lost nor altered.
Immutable audit trail
Every action — view, QR generation, signature capture, sealing, download — enters a hash chain. Not even administrators with direct database access can alter it without leaving a trace.
Offline-verifiable manifest
The sealed document includes the full timeline with chaining hashes. Whoever receives the PDF verifies integrity in any validator, without accessing the platform.
Real isolation between companies
Separation between organizations is enforced by the database itself (Row-Level Security), not just the application. A coding flaw is not enough to leak one client's data to another.
White-label for your client
The signing page shows your company's brand. Emails carry your logo, in each signer's own language — Portuguese or English, set per person.
ERP integration
Webhooks fire when the document is completed and sealed, automating billing, archiving and internal workflows without manual work.
Security you can audit
Security is not a list of badges: it is design. These are structural decisions in JustSign, all verifiable.
- A URL is never proof of entitlement: every document access re-validates authorization at access time
- Documents stored encrypted, with download links that expire in 60 seconds
- Everything recorded in independent hash chains: documents, accounts and negotiation
- Second factor required for platform administrator accounts