Re: [vox] MD5 Checksums and Public Downloading

[Micah Cowan <micah@cMAPSowan.name>]

On Thu, 2002-05-16 at 00:13, Peter Jay Salzman wrote:
> begin Micah Cowan <micah@cowan.name> 
> > Can somebody explain to me what the point is for generating checksums
> > for verifying downloaded files?  If the primary purpose is security,
> > what is to prevent a malicious person, either "man-in-the-middle" or
> > someone who tampered with a repository, from generating a new MD5 sum
> > for you to verify?  What exactly does the checksum prevent?
>  
> i think the point here is a preponderance of evidence.  md5sums are
> usually published in a variety of places, and it would be hard for said
> malicious person to tamper with the whole bunch of them.

H'm...  I must have been seeing them in different places than you,
then.  I sometimes see MD5 sums simply distributed side-by-side with the
software they checksum; in fact, it was on seeing this that I posted to
the group (no, I don't remember what software it was).

> > If the primary purpose is simply to guard against corrupt data, I'd
> > hardly think it worth the effort, considering I very rarely get
> > corrupted data.
> 
> you're probably right here, but i think the keyword here is "i" (or
> rather "you").  other people may not be so lucky.  certainly back in the
> 80's when i was using a modem to transfer \/\/arez, errors were pretty
> common place.  modems didn't have error detection like they do today.

People have pointed out that it's useful for very large files, which I
wasn't really considering, and can certainly understand.  I was mostly
interested in its intended purpose for security, really - as I'm having
trouble seeing how that purpose is served.

-Micah

_______________________________________________
vox mailing list
vox@lists.lugod.org
http://lists.lugod.org/mailman/listinfo/vox