Formats and signature types
Formats and signature types
This page explains which files Autogram can sign and display, and which signature it creates. You do not need it for everyday signing: Autogram picks a suitable format by itself.
What Autogram displays
You can sign any file. Before signing, Autogram can display:
- PDF,
- PNG and JPEG images,
- text files,
- HTML,
- Slovak government electronic forms (XML), shown in a human-readable form.
Other files, such as Word documents, are signed without a preview and Autogram warns you about it.
A password-protected PDF cannot be signed; remove the password first.
Signature types
Autogram creates signatures of three types:
| Type | Where the signature is | When it is used |
|---|---|---|
| PAdES | inside the PDF; the result is a PDF again | by default for PDFs |
| XAdES | in an ASiC-E container together with the document | for all other files, and for PDFs depending on the settings |
| CAdES | in an ASiC-E container together with the document | for PDFs depending on the settings |
PAdES is generally accepted and the easiest: you can open a signed PDF in any PDF viewer. Some authorities, however, require XAdES or CAdES. Change the signature type for PDFs in Settings with PDF signature type.
If a document already has a signature, Autogram adds a signature of the same type and ignores the setting.
ASiC-E container
An ASiC-E container (.asice extension) is a file that holds the signed document and its signatures. It can also hold several documents signed together, see Several documents in one container.
You open and verify a container in Autogram. You can get the document out of it even without Autogram: the container is a ZIP archive, so after renaming it to .zip you can extract it.
Government electronic forms
Slovak government forms (for example from slovensko.sk) are XML files, often wrapped in an XML Data Container. Autogram displays them in a human-readable form according to the form’s template and signs them with a XAdES signature in an ASiC-E container, as authorities require.
Financial Administration forms, such as tax returns, are most often signed directly on the Financial Administration portal with the browser extension or in an application that sends them to Autogram. How developers do this is described in Integration through the HTTP API.
By default, Autogram does not sign an XML file that is not such a form. If you need to sign it, turn on Signing unknown XML in Settings.
Timestamps
A timestamp from a trusted provider confirms that a signature existed at a certain time. With it, the signature stays verifiable even after the certificate expires. In Slovakia, a qualified electronic signature with a qualified timestamp does not have to be certified.
A signature with a timestamp has the BASELINE_T level (for example PAdES-BASELINE-T), a signature without one BASELINE_B. Autogram does not add timestamps by default. How to turn them on and where Autogram gets them is described in Signature with a timestamp.
PDF/A
PDF/A is a version of PDF for long-term archiving that some authorities require. Autogram does not convert PDFs to PDF/A; it only warns you if the signed document does not comply. You can create PDF/A, for example, when exporting to PDF from a word processor.