SHA-1 CHECKSUMS
SHA-1 is the successor of MD5 ( Read about MD5
here ) and is a tool to check the integrity of your downloads.
The SHA-1 algorithm is the brainchild of the US-based National Security Agency (NSA)
Basically it works the same as the MD5, a SHA-1 file is available on the FTP server where you downloaded your ISOs and when opening it you will see a string of numbers that you compare to the output of the command:
You compare it to the string you find in the SHA-1 file on the FTP mirror. If both of them are identical you can be sure your downloaded ISO is okay and you can burn it to a CD.

Bruno
NOTE: Windows users can download a tool Here to check MD5 and SHA1 hashes. ( works in all flavors of windows )
-- Jun 21 2005 ( Revised Dec 9 2005 ) --