0900 940 910 (€ 1,09/min)
Monday through Friday (working days)
from 8:00 am to 6:00 pm


You can find frequently asked questions here

Do you have any questions/problems with your Handy-Signatur?

Contact our Support! Our Support is available to you Mondays to Fridays (weekdays) between 8:00 am - 18:00 pm. The Support can be contacted via our fee based hotline (€ 1.09/min) and free of charge by email at  
Also take a look at our FAQ, where you can find the answers to the most frequently questions. On our statistics page you can also get a live picture of whether the Handy-Signatur is technically running smoothly.
* A-Trust Support takes the time needed to provide detailed, individual and technical answers to customer questions. The service of the telephone service hotline is therefore time-consuming and costly - hence a call to the service hotline is fee-based, in order to meet every telephone request and to guarantee the quality of the service. E-mail inquiries, however, are free of charge and receive the same service coverage.

Revocation service

Unfortunately, it is not possible to provide technical support at this number, because part of the revocation hotline is operated by an external call centre.

Revocation service for user certificates
(e.g. a.sign premium)
Rund um die Uhr - 365 Tage im Jahr
Revocation service for 

Rund um die Uhr - 365 Tage im Jahr
Revocation service for 
Server certificates
Mo - Fr: 10 - 18 Uhr
Revocation service for developer certificates Mo - Fr: 10 - 18 Uhr

Card test

A-Trust directory service

Verify quickly, simply and securely whether certificates by A-Trust have been issued to persons, an e-mail address or a server. 

Directory service