ASiC

ASiC bundles a document with its electronic signature or seal in a ZIP-based container, used when the document format cannot hold one itself.

ASiC (Associated Signature Containers) is the ETSI standard (EN 319 162) that defines a container format for packaging one or more signed data objects together with their signatures into a single file. Unlike PAdES, where the signature is embedded inside the PDF it covers, ASiC wraps a signature that was produced separately - typically CAdES or XAdES, or a qualified electronic timestamp - around data that has no signing mechanism of its own: a plain text file, an image, a set of several files, or an XML document signed as a whole rather than internally.

The standard defines two baseline shapes, distinguished by how many files they cover:

• ASiC-S (Simple): one signed data object plus one signature or timestamp, typically saved with the .asics extension.
• ASiC-E (Extended): one or more data objects plus a manifest that lists what each signature covers, typically saved with the .asice extension; it commonly carries XAdES so that several files can be signed together.

Structurally, an ASiC container is a ZIP archive with a META-INF folder alongside the original data: signature.p7s for a CAdES signature, signatures.xml for XAdES, or timestamp.tst for a timestamp token. This is what lets a qualified trust service provider sign or seal file types that eIDAS's own reference formats would otherwise not cover, while keeping the result verifiable with the same signature validation logic used for CAdES and XAdES.

Note: ASiC is not a fifth signature format alongside CAdES, XAdES and PAdES - it is a wrapper around one of those. Renaming a .asics or .asice file to .zip and opening it in an ordinary archive tool shows exactly this: the original file plus a META-INF folder, because that is literally what the container is.