[Opensim-dev] Proposal to eliminate the name, description and invType fields from the assets db table

[Melanie]

What is the purpose of creating UUIDs by hashing? If it's not 
duplicate detection/prevention, I see no reason. GUIDs are supposed 
to be random, I believe.

Melanie

Sean Dague wrote:
> On Sat, Jun 21, 2008 at 09:41:33PM -0400, Frisby, Adam wrote:
>> Snip:
>> ---
>> ...Moreover, if we adopt generation of UUIDs using a hashing algorithm
>> (e.g. SHA1) at some stage, we wouldn't even need to embed the UUID in
>> the name...
>> ---
>> Unsnip:
>> 
>> A warning here if I may.
>> 
>> *DO NOT DO THIS*. Hashing to produce a UUID for the asset, while
>> tempting in a space-saving kind of way, actually is not secure. Allow me
>> to explain further:
>> 
>> There are many known attacks on MD5 (and SHA1) which allow a duplicate
>> hash to be produced by tacking on additional data at the end of your
>> intended data, so - say someone wants to replace the default avatar with
>> a flying phallus, it would be possible to do, by creating a specifically
>> targeted asset with some dummy data on the very end to produce a
>> duplicate hash. When uploaded, it would override the original UUID of
>> that asset and hence could be bad.
> 
> First off, SHA1 isn't broken.  Secondly, we have a no update policy on
> assets today, so this isn't a viable attack even if it was broken.
> 
> I don't think that with those 2 facts using SHA1 would be an issue
> here.  I'd like to avoid SHA256 if possible, mostly because SHA1 is
> computationally fast.
> 
> While I understand the hype on the concerns here, the way we'd use SHA1
> generated UUIDs shouldn't open up any holes.
> 
>     -Sean
> 
> 
> 
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