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+
+- Directory structure:
+ - Encrypted user data (catfiles) are stored in the usual /data/user/files dir
+ - Keyfiles are stored in /data/user/files_encryption/keyfiles
+ - Sharekey are stored in /data/user/files_encryption/share-files
+
+- File extensions:
+ - Catfiles have keep the file extension of the original file, pre-encryption
+ - Keyfiles use .keyfile
+ - Sharekeys have .shareKey
+
+Shared files
+------------
+
+Shared files have a centrally stored catfile and keyfile, and one sharekey for
+each user that shares it.
+
+When sharing is used, a different encryption method is used to encrypt the
+keyfile (openssl_seal). Although shared files have a keyfile, its contents
+use a different format therefore.
+
+Each time a shared file is edited or deleted, all sharekeys for users sharing
+that file must have their sharekeys changed also. The keyfile and catfile
+however need only changing in the owners files, as there is only one copy of
+these.
Notes
-----
- The user passphrase is required in order to set up or upgrade the app. New
keypair generation, and the re-encryption of legacy encrypted files requires
it. Therefore an appinfo/update.php script cannot be used, and upgrade logic
- is handled in the login hook listener.
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+ is handled in the login hook listener. Therefore each time the user logs in
+ their files are scanned to detect unencrypted and legacy encrypted files, and
+ they are (re)encrypted as necessary. This may present a performance issue; we
+ need to monitor this.
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