To ensure integrity of the data that the DS‑Client backs up and restores on a customer network, a digital signature is created and attached to every file that DS‑Client transfers to the DS‑System. A digital signature represents 128‑bit code that identifies data within the file. Even a one‑bit change to a file will produce a different digital signature.

Digital Signatures are used for the processes described below.

During a restore operation, the DS‑Client recreates the digital signature and compares it to the one attached to the file. This verifies that the file content is exactly the same as that which was backed up. This is especially important when restoring databases, Registry, NDS and other types of data where even one‑byte changes can make the data useless or even harmful.

Validation uses the Digital Signature to verify the integrity of the online file. For more information, see the Knowledge Base article in “Validation Overview”.

[Windows DS-Clients only]

During a Demand Backup, you have the option to select Verify signature for unchanged files. This feature is intended as a troubleshooting tool. If you use it, DS-Client will read the digital signature from the latest online generation of each unchanged file, and compare it with the digital signature that is generated from the current source file. If the signatures do not match (this should not occur often, or even at all), DS-Client will re-backup that file in that same backup session.

If you use this feature, backup performance will slow by a significant amount, since the files that would otherwise be ignored must be processed.