[Standards-JIG] Unique room names for JEP-45

Robert B Quattlebaum, Jr. darco at deepdarc.com
Sat Jun 17 01:10:26 UTC 2006


On Jun 16, 2006, at 2:25 PM, Kevin Smith wrote:
> On 16 Jun 2006, at 21:25, Robert B Quattlebaum, Jr. wrote:
>> In other words, when there is a 1 out of 2^128 chance that there  
>> will be a collision, I don't think that it is "correct" to check  
>> for collisions. It is redundant.
>
> Million to one chances turn up nine times out of ten.

I'm sorry, but that doesn't make sense. Also, we aren't talking about  
million (1x10^6) to one chances. We are talking about something much,  
much larger...

2^128 = 340282366920938463463374607431768211456 ~= 3.4x10^38

Due to the birthday paradox, we can approximate the chances of a  
collision between values to be approximately:

1 - (e^(-(n^2) / (2 * (2^128))))

where

n = number of samples.

Assuming every person on the face of the planet (~6 billion) created  
a 'nameless' conference room on a single MUC server, the chances of a  
collision are (approximately):

1 out of 18,904,575,940,052,136,859 (1.89x10^19)

For all practical application, I think we can assume collisions to  
not be a problem.

That being said, I'm not against having the server choose a name for  
us. I just don't want you to think that doing collision checks when  
dealing with probabilities on this magnitude is a matter of  
correctness. It is effectively a redundant operation.

__________________
Robert Quattlebaum
Jabber: darco at deepdarc.com
eMail:  darco at deepdarc.com
www:    http://www.deepdarc.com/


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