or you could just creat a password protected zip file. I don't know how well the unzip program for linux handles the password protection, but still.
YES, there are many problems that would just break the encryption of the zip... and yes, the PGP is pretty hard to decrypt... but it's still possible. And anyone with the knowldege to brak a zip encryption could find a way to break a pgp (not easy, but possible).
Anyway, what's so important? I mean... if it REALLY is important to avoid any kind of violation, then just burn it to a CD-R and keep it in a safe place... As long as it's in any digital media a person has access, it's possible to decrypt it. Even the Shadow encryption is possible to break. (through brute force, but still possible)