Re: Create on insert a unique random number

On Mar 18, 2008, at 1:40 PM, Campbell, Lance wrote:

> Thanks for all of your input. It appears that the best way to do this
> is to create a default random number in the primary id field in the
> table definition and then return that value after insert. If an
> exception occurs because of duplicates I will simple perform the same
> insert statement again. I doubt there would be many duplicate hits
> if I
> use a really large number.
>
> Why use a random number as a primary key? Security via obscurity.
>
> I build web applications for a living. In most of my applications
> it is
> preferable to use a random primary key. Why?
>
> Example:
>
> I built a web application called the Form Builder. It allows
> individuals to create web forms. After a user is done building their
> web form the tool provides a URL for the user to access the form.
> Obviously the URL has the random ID of the form in it. Most of the
> forms created with this tool can be accessed and filled out by the
> general public.
>
> So why not use a sequential number? So if I used a sequential number
> then a student or outside individual could easily change the number in
> the URL to see what other forms there are. It is not that they don't
> have access to the forms but they should not be messing with them if
> they really don't have a reason to. So by using a very large random
> number the users filling out a form cannot easily guess what another
> form ID is.
>
> Does that make sense? I have at least a dozen tools that I prefer to
> use this approach on.
>
> This is not a security approach. It is more about not giving obvious
> access to people that want to mess around.

I'd say it makes total sense and we do much the same thing with
unsubscribe links in the emails we push here. However, we keep the
primary key based on sequences and for sent messages generate a random
id using md5(now()::text). In a sense, then, we have "public" and
"private" keys.

Erik Jones

DBA | Emma®
erik(at)myemma(dot)com
800.595.4401 or 615.292.5888
615.292.0777 (fax)

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