Enigma Plugin for Roundcube

This plugin adds support for viewing and sending of signed and encrypted
messages in PGP (RFC 2440) and PGP/MIME (RFC 3156) format.

The plugin uses gpg binary on the server and stores all keys
(including private keys of the users) on the server.
Encryption/decryption is done server-side. So, this plugin
is for users that trust the server.

WARNING! The plugin is in very early state. See below for a list
of missing features and known issues.


Implemented features:
---------------------
+ PGP: signatures verification
+ PGP: messages decryption
+ PGP: Sending of encrypted/signed messages
+ PGP: keys management UI (keys import and delete)
+ Handling of PGP keys attached to incoming messages
+ User preferences to disable plugin features

TODO (must have):
-----------------
- Keys export to file
- Disable Reply/Forward options when viewing encrypted messages
  until they are decrypted successfully
- Handling of replying/forwarding of encrypted/signed messages
- Client-side keys generation (with OpenPGP.js?)

TODO (later):
-------------
- Handling of big messages with temp files
- Server-side keys generation (warning: no-entropy issue, max_execution_time issue)
- Key info in contact details page (optional)
- Extended key management:
   - disable,
   - revoke,
   - change expiration date, change passphrase, add photo,
   - manage user IDs
- Generate revocation certs
- Search filter to see invalid/expired keys
- Key server(s) support (search, import, upload, refresh)
- Attaching public keys to email
- Mark keys as trusted/untrasted, display appropriate message in verify/decrypt status
- Change attachment icon on messages list for encrypted messages (like vcard_attachment plugin does)
- Support for multi-server installations (store keys in sql database?)
- Per-Identity settings (including keys/certs)
- Performance improvements:
   - cache decrypted message key id so we can skip decryption if we have no password in session
   - cache (last or successful only?) sig verification status to not verify on every msg preview (optional)
- S/MIME: Certs generation
- S/MIME: Certs management
- S/MIME: signed messages verification
- S/MIME: encrypted messages decryption
- S/MIME: Sending signed/encrypted messages
- S/MIME: Handling of certs attached to incoming messages
- S/MIME: Certificate info in Contacts details page (optional)

Known issues:
-------------
1. There are Crypt_GPG issues when using gnupg >= 2.0
   - http://pear.php.net/bugs/bug.php?id=19914
   - http://pear.php.net/bugs/bug.php?id=20453
   - http://pear.php.net/bugs/bug.php?id=20527