LTA

LTA is the ETSI baseline signature level that adds renewable archive timestamps to keep signatures verifiable for decades.

LTA (Long-Term Availability and integrity of the validation material) is the highest of the four baseline levels defined by the ETSI AdES signature formats (CAdES, XAdES, PAdES, JAdES). It builds on B-LT, which embeds the certificate chain and revocation data needed for validation, by adding one or more archive timestamps that cover the signature, the certificates and all earlier validation data in a single cryptographic envelope.

The point of an LTA timestamp is renewal: as a certificate's validity period ends, a CRL or OCSP response ages out, or a hash or signature algorithm weakens, a fresh archive timestamp is applied over everything that came before, re-anchoring integrity to a new, trusted moment. Repeating this before each element expires is what keeps a document verifiable for decades - the practical mechanism behind long-term validation (LTV).