Simple checksums don't really help -- they are easy to duplicate in any arbitrary file. To be of any use, one would need to include a message digest (a.k.a., secure hash) such as MD5 or Snefru. That raises problems of standardization, portability, and cpu cycles. Plus, what do you do it on? The source file? The compressed file? The gzip'ed file? Each would give a different value, and not every site has all three. If you want to uncompress each file, run Snefru on it, then delete the decompressed version, we are talk serious CPU load.... If you want more info, you can see some of the discussion of checksums and message digests in the Tripwire design document, and the references it cites. --spaf