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Sign Documents

Digital signatures prove that a document came from you and hasn't been tampered with. Qpher Vault uses Composite ML-DSA (ML-DSA-65 + ECDSA P-256) — a quantum-safe signature algorithm standardized by NIST.

Why Sign Your Documents?​

  • Authenticity — proves the document came from you
  • Integrity — detects any tampering after signing
  • Non-repudiation — you cannot deny having signed the document
  • Quantum-safe — signatures remain valid even against quantum computers

Sign a Document​

  1. Open the document detail page
  2. Tap the menu button (three dots) in the top-right corner
  3. Select Sign Document
  1. Review the signing confirmation
  1. Tap Sign — the server signs the document with your ML-DSA key

Verify a Signature​

Signed documents display a Signed badge on the document list and detail page:

The signature is verified server-side every time the document is accessed. If the document has been tampered with, the signature verification will fail and you'll be alerted.

Signing key security

Your signing private key is stored in the server-side KMS and never leaves the secure environment. Only you can initiate a signing operation through the app.

Plan Requirements​

Digital signatures require the Personal plan or higher. Explorer (free) users can view signed documents but cannot create signatures.