Re: CRC32 module?

[Rob Kendrick <lua-l@...>]

PA wrote:
> On Feb 07, 2005, at 11:56, Luiz Henrique de Figueiredo wrote:
>
> > Do you really need CRC32?
>
>
> Yes.
>
> >  Doesn't MD5 or SHA1 work for you?
>
>
> Yes. But for different purposes.
>
> For example, lets assume I want to build an URL pointing to some data of 
> some sort. The data are uniquely identified by a time based UUID:
>
> 98ab2edf-ef9c-42e3-a4cc-739442ce2186
>
> A md5 of an uuid is still quite long and obscure:
>
> cfcd208495d565ef66e7dff9f98764da
>
> So... what I would like to do instead is to build an URL which reflects 
> the UUID time, plus a short hash to identity the data in that time frame:
>
> /2005/02/07/12345
>
> Therefore the need for some predictable hashing of some sort. CRC32 
> comes to mind. But any sort of hashing would do. Doesn't Lua itself have 
> some kind of hashing function for strings?

This'd make me very uneasy - it's too easy to predict CRCs, which may 
lead to a security flaw later on.  A better choice would be to just take 
the first 6 characters of a SHA1 or similar.