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Reinaldo de Carvalho wrote:
> Is there a way to encrypt all of the Cyrus' user-specific files on the disk?So that somebody breaking in -- or stealing the server -- has no access to the messages (and other data) unless a user's password is also available?Use a encrypted file system to protect data from steal. GPG is the real solution because any server encryption suffers chicken and egg problem.
Encrypted file systems have the disadvantage of having to be manually mounted. So, a server reboot will not restore the IMAP-service automatically. This is not a limitation of a particular implementation, but simply an inevitable part of the requirement -- any automatic procedure will leave the data just as open as with an unencrypted FS, because a stolen server will repeat the procedure upon boot in whosoever's hands it is booting. You could only hack something together by storing the procedure (or a key-component thereof) on a different system, but even then convincing (or coercing) the admin would give access to all e-mails at once...
The other disadvantage of relying only on the encrypted FS for this purpose is that all messages are open, while the FS is mounted, so a successful hacker (or coercer) penetrating the server at runtime would have access to everything.
The proposed method uses each user's own password to encrypt their mails -- only the mailboxes of the currently-connected users would be exposed to a hacker (or coercer).
PGP, while great, is not an all-covering solution, because it requires users -- and all their correspondents (!) -- to switch to PGP as well. That's not an option for many, if only because Yahoo!'s and Google's services don't support it. Neither do any of the online merchants, for another example of a substantial source of e-mails today.
The proposed method would be entirely on the server, requiring no cooperation from the user nor their MUA.
I'm unaware of the "chicken and egg problem" inherent in server encryption. Perhaps, you can expand on it? If that's what I think you are referring to, my proposal deals with it -- newly arrived messages remain unencrypted until the next time the user logs in. However, they are no worse off, than while still traveling over the Internet, but the user's archives are now protected.
I think, my proposed method should be viewed as complimenting the measures you mention. A particular setup can combine any subset of them.