Re: How unique is SID?
| From: | Sascha Schumann | Date: | Tue, 29 Aug 2000 08:29:46 +0000 |
| Subject: | Re: How unique is SID? | ||
| References: | 1 | Groups: | php.general |
| Request: | Send a blank email to php-general+get-14071@lists.php.net to get a copy of this message | ||
On Mon, 28 Aug 2000, Mika Tuupola wrote:
>
> How unique is session id created by session_start()?
> If I plan to save data on disc and am considering
> the session id as a filename will I get into trouble,
> ie. what is the probability of overwriting previous files
> if there happens to be a duplicate sid over period of
> time?
>
> If session id:s are not unique then date + sid combination
> is probably sufficient?
I suggest educating yourself about "entropy".
The theoretical probability that MD5 produces a collision is
1/(2^128) (translates to very unlikely).
- Sascha