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Sign Documents

Sign a document with ML-DSA in your name before you share it; recipients see that it is signed.

What a signature shows​

  • Authenticity — the document was signed with your Qpher key
  • Integrity — any change after signing makes the signature fail to verify

ML-DSA and SLH-DSA signatures are designed to resist forgery by a quantum computer.

Sign a document​

  1. Open the document page
  2. Tap ⋮ and choose Sign document (Sign again if the document is already signed)
  3. Tick I agree to digitally sign this document and tap Sign Now
  4. Confirm with Face ID or your passcode. Qpher signs the document with your key inside its isolated key service

When you encrypt a document, Sign this document is on by default, so new documents are signed as they are saved.

For a document shared with you with download permission, the same menu offers Counter-sign, which adds your signature.

Algorithms​

The default is a composite signature — ECDSA P-256 + ML-DSA-65, a hybrid built on an IETF draft (ML-DSA is NIST FIPS 204). On every plan except Free, the sheet's Signing Mode also offers Archive (SLH-DSA, NIST FIPS 205) and Composite (ML-DSA-65 + SLH-DSA-192s).

The Signed badge​

Signed documents show a Signed badge in your list and on the document page. It means a signature is on record; Qpher Vault does not re-check the signature each time you open the document.

Organizations

If you belong to an organization, documents are signed with the organization's key. The signature shows the document came from the organization; the document and its access log show which member signed. If a member joins or leaves the organization after signing, verifying through Qpher may fail.

Verifying a signature through Qpher needs the signing key to be active or retired; once a key is archived, Qpher can no longer verify its signatures.

Plans​

Signing and counter-signing work on every plan, including Free. The Archive and Composite signing modes need a paid plan.