Created by: Wikinaut
I file this as suggestion to overcome several problems with the server-side encryption of pre-4.5 versions.
Situation ownCloud (as far as I understand it)
- when using the server-side encryption, you cannot share files. Files are encrypted per single key for all files in the user directory. Sharing would require to pass the key to the person with whom you want to share the file.
- http://sebsauvage.net/wiki/doku.php?id=php:zerobin is a opensource online pastebin/discussion board where the server has zero knowledge of hosted data. Data is encrypted/decrypted in the browser using 256 bits AES. See also http://www.heise.de/security/meldung/Interessantes-Konzept-fuer-verschluesselte-Pastes-1541988.html
- http://gpg4browsers.recurity.com/ and http://www.openpgpjs.org/ (new ) and http://www.heise.de/newsticker/meldung/OpenPGP-im-Browser-1381826.html
Using the mentioned techniques it would become possible
- to have a possibility for a platform independent (browser-) client-side encryption and decryption of files. All data traffic to the server would be encrypted, all files are only stored encrypted on the server, and no server-side encryption will be necessary any longer.
- to assign all users a user key (each user has their own user key), and all their files got encrypted (client-side) with their specific user's key
- to share (encrypted) files, given that they are encrypted with more than the key of the user, for example the user key and a key for another user, or for another group who shares one group key.
- enterprise users, where in enterprises usually the installation of additional software is prohibited, can participate as any other user, because the en/decryption takes place in their browsers and does not require installation of any software (GPG, openPGP, ...) except a contemporary HTML5 browser which is capable to run the client-side crypto algorithms.
- all traffic is encrypted
- no plain files on the server
 http://www.dp-dhl.com/en/media_relations/press_releases/2012/docwallet_documents_manager_for_the_ipad.html Deutsche Post AG end-to-end AES-256 encryption for documents  http://www.heise.de/ct/inhalt/2013/02/42/ "PDF-Tresor von der Post" article in "c't" 2013/2 page 42
 https://github.com/toberndo/mailvelope/issues/45 regarding private key security
I just found these cloud services claiming to offer end-to-end encrypted cloud services