Le dimanche 2 février 2003, à 01:33 , Douglas Stemen a écrit :

> It is critical that I keep users from easily opening these files. Can 
> someone tell me how to do this?

it seems to me that you were relying on 'obscurity' as your principal 
security mechanism here. ie, the info is there, in plaintext, but you 
just don't let the users read the files. like invisible files, hiding in 
resources and so on, this is a method guaranteed to fail.

all security experts will tel you that obscurity is not good.

you have an accounting application. it is probably a good thing for the 
user that the data files are readable in a plaintext application. this 
is just for the simple expedient that if you disappear one day and the 
app no longer functions, a script can be devised that will read back the 
data and massage it for another accounting app.

i'm supposing that the passwords that are revealed prevent an 
unauthorised user from accessing the data/your app. and your rightly 
feel that having a password [visible] is not good if joe anyone can just 
open the data files anyway and read the contents, or just stumble on the 
data.

this means that you are going to be faced with a number of issues:
- secure entry protection [i'd suggest keychain as number one, encrypted 
keyword as number two] combied with the mac os x feature of having an 
account per user, so that someone with 'guest' access on the 
accountant's machine cannot access the data files anyway [repeat after 
me, never use root access in X, always create an account for yourself].
- data protection, this will mean that you need a proprietary data 
format and preferably one that scrambles the data in such a way that -- 
a) it is unrecognisable and not easily used, b) can be unscrambled so 
that you can use it.

a proprietary format on its own is no protection. ms do not publish the 
format used by msword documents -- that doesn't stop people from 
reverse-engineering it and creating msword-readers [very useful btw]. 
you will need both a format and revisible crypto. it would also be 
useful [see the issue earlier of transferring info to another app] of 
having an export function that does allow the user to export plaintext 
files.

:-j