S 5.67 Use of a time stamp service

Initiation responsibility: IT Security Officer, Head of IT

Implementation responsibility: User, Administrator

The time information contained in the header of an email may be manipulated relatively easily. If it is necessary to know the exact times an email was sent and received, a time stamp service must be used. A time stamp is a time input made by a neutral office that can no longer be falsified. It is either applied fully automatically by a time stamp server, i.e. transparently for the user, or upon request of the sender.

A time stamp consists of the time stamp certificate used to document the current date and the current time, as well as the identity of the time stamp service, and of a digital signature via email and certificate. This way, the time stamp documents and confirms the existence of a certain message with a certain content at a certain time. Ensuring the authenticity of the email with the help of the time stamp requires that the sender signed the email.

A time stamp service may be offered and used in an internal network and on the internet. As a server on the internet/intranet, it accepts files signed or only their signature and equips these with a synchronised time stamp. This is in turn signed by the time stamp service and forwarded to the recipient or returned to the sender alternatively.

Review questions:

© Federal Office for Information Security. All rights reserved.