# ASiC-E file format: the structure of the container

> The ASiC-E file format is defined by a European standard and built from two familiar technologies: ZIP archives and XML signatures. This is a compact technical overview.

Source: https://asiceviewer.com/en/blog/asice-file-format/
Published: 2026-11-10 · Digixy

## In short

- Standard: ETSI EN 319 162-1, Associated Signature Containers.
- Physically a ZIP archive; logically data files plus detached signatures.
- Signatures are XAdES (XML) or, less often, CAdES (binary).

## The standard

ASiC stands for Associated Signature Containers. The specification, ETSI EN 319 162-1, describes how to bind one or more files to signatures or time stamps inside a single archive. It defines two forms:

- **ASiC-S** (Simple): exactly one data file with its signature or time stamp.
- **ASiC-E** (Extended): any number of data files and any number of signatures.

ASiC is among the formats that public bodies in the EU must accept under the eIDAS implementing rules.

## Physical layout

| Entry | Required | Content |
| `mimetype` | Recommended, first and uncompressed | `application/vnd.etsi.asic-e+zip` |
| Data files | Yes | The signed documents, in the root or in folders |
| `META-INF/manifest.xml` | With XAdES | OpenDocument-style list of files and media types |
| `META-INF/signatures*.xml` | With XAdES | One `XAdESSignatures` document per signature |
| `META-INF/ASiCManifest*.xml` | With CAdES | References and digests of data files |
| `META-INF/signature*.p7s` | With CAdES | Binary signature over the ASiC manifest |

## How a signature is bound to files

With XAdES, every signature holds a `ds:Reference` for each data file: the file's URI in the archive and its digest, typically SHA-256. The signer's private key signs the block containing those digests. Change one byte of any file and its digest no longer matches.

With CAdES the indirection is explicit: an `ASiCManifest` lists the digests, and the binary signature covers that manifest.

## Baseline levels

| Level | Adds |
| B-B | Signature, signing certificate, signed properties |
| B-T | Time stamp over the signature |
| B-LT | Certificates and revocation data for long-term validation |
| B-LTA | Archive time stamps for long-term preservation |

## Related formats

BDOC 2.1 is an Estonian profile of ASiC-E with XAdES; EDOC is the Latvian equivalent. They share the layout, which is why one viewer opens all of them. DDOC is the exception: an older single XML file rather than a ZIP.

## Seeing it in practice

Drop a container onto [ASiCE Viewer](https://asiceviewer.com/en/#tool) and open **Technical files** to browse `mimetype`, the manifest and each signature as formatted XML. To follow the same steps with command-line tools, read [ASiC-E file reader](https://asiceviewer.com/en/blog/asice-file-reader/).

## Frequently asked questions

**Is ASiC-E an open format?**

Yes. It is a published ETSI standard built on ZIP and W3C XML Signature, and anyone may implement it.

**What is the MIME type of an ASiC-E file?**

application/vnd.etsi.asic-e+zip. The simple form uses application/vnd.etsi.asic-s+zip.

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