Encrypting files for many users..

[Arnaud Ongenae]

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OpenPGP is a protocol essentially oriented to the exchange of
information. But can also be used to protect file on your own
computer.

You can encrpyt one file for many users, it is usually the case when
you encrypt one message:

example:
Alice want to send a message 'm' to Bob
Alice encrypt his message 'm' with both her key and Bob's key E_{a, b}(m)
By doing this Alice can read her own message later.
Bod will decrypt it with his private key D_b(E{a, b}

So to come back to your problem, do you want to exchange data ? if so,
you can encrypt this data to all the person you want with their public
key...
And when an user is added or remove, you simply encrypt the new
message with or without his public key...

But if you plan to share some space with encrypted files, and you want
people to be added or removed to this sharing, you must re-encrypt the
files with all the current keys wich I thing is a bit annoying if you
have a lot of persons who can access the sharing and a lot of files...

Another important point is that each accessing person must have a
public/privat key...

Your big problem is 'remove' people, cannot those people access data
there were allowed in the past an only be restricted to the new files
? it could considerably simplify thing !

_-Arnaud-_

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On Wed, Jun 11, 2008 at 7:13 PM, Sartoros Dionysios
<Dionysios.Sartoros at spvm.qc.ca> wrote:
>
>
> Hey,
>
> Question for you guys, new gnupg user here, great software..
>
> I was thinking of maybe encrypting files in PGP that many people will
> require access to, since i dont know PGP inside and out I was wondering
> what would be the best method, as sometimes I will have to remove access
> for some users and add new users
>
> I dont know subkeys or how pgp works with files too well.. Can i
> add/remove users' keys to encrypted files.. If i have 100 or even 1000
> files, would I have to do it one by one (to add a new user or remove
> access to one)..
>
> Thanks
> Dennis
>
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