Probably a global attribute could be used to assign the checksum file. Or s ome other trick to get the right checksum file. Then it is nearly the same if the data is inside the netCDF file or in a separate file. Reimar Am Samstag, 5. Februar 2005 17:38 schrieb Gerry Creager N5JXS: > It can go both ways. If the file's corrupt because either the hash was > modified and the data were intact, OR if the data (plus/minus the hash) > were modified, it's still bad. > > Then again, keeping an external hash in another file may allow one to > determine whether the data, or the hash were modified. > > The benefits derive, IMO, from the point of view of data source. If you > control the data, and you're concerned about programmatical mods causing > problems, the external method has benefits. > > If you're concerned about data security and integrity, the former > approach, allowing you to simply say, "It's bogus, let's attempt to get > it from another source," has promise. > > For simplicity, I'd agree that a separate file approach is an acceptable > one. > > gerry > > Russ Rew wrote: > > I wrote: > >>I think there are some good reasons to keep hashes such as MD5 or > >>SHA-1 external to files they are intended to check, rather than > >>embedded in the files: > >> > >> - If the digest is external, then something that corrupts the file > >> might also corrupt the digest. > > > > which makes no sense. What I meant to say was > > > > - If the hash is embedded in the file and doesn't agree with the > > file contents, it's not clear whether the file or the hash or both > > were corrupted. > > > > This is fairly minor, since a mismatch would tell you not to trust the > > data in any case. But I still think keeping the hash separate from > > the original file makes it easier to compute. > > > > --Russ -- Forschungszentrum Juelich email: R.Bauer@xxxxxxxxxxxxx http://www.fz-juelich.de/icg/icg-i/ ========================= ========================= ================ a IDL library at ForschungsZentrum Juelich http://www.fz-juelich.de/icg/icg-i/idl_icglib/idl_lib_intro.html
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