Question:

• How to verify the integrity of downloaded Gigaset firmware?
• How to verify the integrity of the copied Gigaset firmware on your server?

Solution:

Compare the MD5 hash from the copied file and the original file using MD5 checksum. If they are the same, then there is a high probability that the two files are the same.
The MD5 hash can be found on the Firmware page on this wiki.