AdES baseline levels (B-B/B-T/B-LT/B-LTA)

The four conformance tiers shared by all of ETSI's AdES formats.

Definition

B-B (Basic) holds the signature and the mandatory signed attributes. B-T adds a trusted timestamp (RFC 3161) over the signature. B-LT (Long-Term) embeds certificates and revocation data (OCSP/CRL) so it stays verifiable. B-LTA (Long-Term with Archive timestamp) adds renewable archive timestamps for retention beyond algorithm obsolescence.

Origin

Defined consistently across the ETSI ESI standards: EN 319 132-1 (XAdES), EN 319 122-1 (CAdES), EN 319 142-1 (PAdES) and EN 319 162-1 (ASiC). They supersede the legacy -BES/-EPES/-T/-C/-X/-XL/-A naming.

Example in context

A legal e-invoicing archive typically targets B-LTA: the signature is timestamped (B-T), enriched with revocation evidence (B-LT), then sealed with a periodically renewed archive timestamp (B-LTA).

Related terms

• XAdES, CAdES, PAdES — the formats that implement these levels.
• RFC 3161 / timestamp token — the building block of the B-T level.