Files wrongly considered as damaged in encfs volume
I've found the answer here (for BoxCryptor):

Under special circumstances, Mac OS X adds the extended attribute 'com.apple.quarantine' to a file which was e.g. downloaded from the internet. This can also happen to files within the BoxCryptor Folder. If an encrypted file has this extended attribute set, you receive the &quot;is damaged&quot; error message when trying to open the plaintext file in the BoxCryptor Volume.

Also try this, more secure workaround:

x) Open Terminal (Applications -&gt; Utilities)
y) Run the following command (substitute the path):
$ xattr -r -d com.apple.quarantine /path/to/encfs/mount/point