Every check described in the other guides is circumstantial — it makes fraud more or less likely, never certain. 2D-Doc is different: it rests on cryptography, and allows a clear-cut answer.
2D-Doc is a two-dimensional DataMatrix barcode specified by the French ANTS (national agency for secure documents). It appears on tax notices, pay slips, social security certificates, proof-of-address bills from some suppliers, and assorted administrative documents.
It holds two things: the document's key data in clear text (name, amount, date, reference), and a cryptographic signature of that data, produced with the issuer's private key.
Metadata can be rewritten, fonts can be imitated, a scan erases the traces. A cryptographic signature cannot: without the issuer's private key you cannot produce a valid signature over modified data.
That yields two distinct checks, and the difference between them matters:
TrustyFile currently decodes the 2D-Doc and compares the encoded data against the visible text. That is the first check, and it already catches visual edits.
Signature verification itself is not implemented yet. We would rather write that here than imply a guarantee that does not exist: today, no TrustyFile result proves a document is genuine. The tool reports anomalies; it does not issue certificates.
For a French tax notice, the tax administration runs an online verification service (SVAIR) where you enter the tax number and the notice reference. The answer comes from the source itself, which beats any file analysis.
General rule: when the issuer offers a way to verify directly with them, that is always the route to take first.
Edited amounts, altered dates, swapped bank details: the technical evidence that gives away a tampered invoice PDF, and how to check for it.
Utility, telecom and internet bills used as proof of address: the technical checks that reveal an edited document, and when the checks simply cannot apply.
A PDF keeps a record of its successive saves: incremental revisions, ghost objects, two sets of metadata. Where to look to find out whether a file was edited.
Fake pay slips in rental files and loan applications: payroll software fingerprints, arithmetic checks and the French 2D-Doc barcode that expose an edited document.
Payment redirection fraud swaps the bank details on a genuine invoice. IBAN checksum, bank-code consistency and PDF tampering traces: how to check details received by email.
A supplier announces new bank details? How the fraud works, the warning signs in the message and in the attached document, and the checks to run before you pay.
Check a Kbis against the public registers (SIREN, directors, registered office, company status), spot a forged PDF, and know what a genuine Kbis does not prove.
Landlord or agency: verify a tenant's French income-tax notice with the tax office's online service (SVAIR), the signed 2D-Doc code and the other documents in the file.
Checking a French subcontractor's attestation de vigilance: the 15-character security code on urssaf.fr, the six-month validity, and what the law requires of the client.
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