Re^2: Simple Digests?

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Re^3: Simple Digests? by radiantmatrix (Parson) on Mar 29, 2006 at 15:13 UTC
Ah. That's a tough one. Digests can help, but since two very different sets of data can share a digest... well, it won't be unique. You could do something like a digest prepended with the nth 10 bytes from the file, or something, but even that wouldn't be a guarantee. It comes down to finding something that's unique enough about the data that when it's combined with a digest, you have a "pretty much guaranteed" unique key. MIME type, maybe? Combined with a longer digest (say, SHA-256), that would be pretty good. Two different digests (say, `MD5().SHA256()`) would be a likely candidate, too -- the chance that data "A" will have a digest collision with data "B" in two different digest systems is fanstastically small. <-radiant.matrix-> A collection of thoughts and links from the minds of geeks The Code that can be seen is not the true Code I haven't found a problem yet that can't be solved by a well-placed trebuchet	[reply] [d/l]
Re^4: Simple Digests? by pileofrogs (Priest) on Mar 31, 2006 at 02:20 UTC
I really don't need that much protection from collisions. It's not like I need to worry about someone intentionally trying to create a collision. Instead of a 1 in a Zillion odds of a collision, I probably could get by with 1 in a thousand.	[reply]
Re^3: Simple Digests? by shotgunefx (Parson) on Mar 29, 2006 at 21:04 UTC
Are you retrieving it just by the key? If you're using some other data to get the key, you could use a timestamp prefixed to the md5. Seems like it would be pretty tough to have a collision -Lee "To be civilized is to deny one's nature."	[reply]
Re^4: Simple Digests? by pileofrogs (Priest) on Mar 31, 2006 at 02:21 UTC
Freaking Brilliant!	[reply]
Re^5: Simple Digests? by shotgunefx (Parson) on Apr 01, 2006 at 02:02 UTC
Sometimes ;) -Lee "To be civilized is to deny one's nature."	[reply]

Freaking Brilliant!