A signature that verifies today may fail to verify in ten years — not because anyone tampered with it, but because the information needed to check it has expired. For contracts, deeds, medical records and anything that must stand up decades later, that is a serious problem. Long-term validation (LTV) and PAdES archiving solve it by capturing the proof of validity at signing time and preserving it.
Why signatures decay over time
To verify a signature, you need the signer's certificate, proof it was valid when used, and the revocation information current at that moment. Over time, certificates expire, certificate authorities retire, and revocation services go offline. Without preserved evidence, a perfectly genuine signature can become unverifiable — its validity simply can no longer be demonstrated.
How PAdES long-term validation works
PAdES — the ETSI standard (EN 319142) for PDF signatures — defines profiles for long-term validity. At the LT and LTA levels, the signature embeds the full certificate chain and revocation data, then adds a trusted timestamp from a time-stamping authority. The timestamp proves the signature existed and was valid at a specific moment, and the embedded evidence means a verifier needs nothing external to confirm it years later.
Archiving for the very long term
For documents that must survive decades, a single timestamp is not enough — cryptographic algorithms weaken over time. Archive timestamps address this: by periodically applying a fresh timestamp over the existing evidence before older algorithms age out, the chain of proof is continually renewed. This is how a signed PDF can remain demonstrably valid far beyond the life of any single certificate or algorithm.
What to look for
- PAdES LT/LTA support so evidence is embedded, not dependent on external lookups.
- Qualified timestamps from a trusted time-stamping authority.
- Automatic revocation data capture at signing time.
- Archive timestamp renewal for documents with very long retention needs.
HOW PRIMESIGN HELPS
primesign helps organisations preserve the validity and evidentiary value of signed documents long after the original certificates have expired. With PAdES-compliant long-term validation, trusted timestamps, embedded revocation data, and archive timestamp renewal, primesign supports secure document preservation for years or even decades while maintaining verifiable integrity and authenticity.
Need to keep your digital signatures valid for the long term? Talk to primesign about PAdES-based long-term validation and archiving solutions.