LibreOffice Encryption/Decryption Implementation

[Michael Stahl]

On 05.12.19 15:12, Steve Martin wrote:
> Hello,
> 
> my name is Steve Martin and I am a student at Ruhr University Bochum. I 
> have a few questions regarding the implementation of encryption and 
> decryption process in LibreOffice. I found some informations at:
> 
> http://docs.oasis-open.org/office/v1.2/os/OpenDocument-v1.2-os-part3.html#__RefHeading__752815_826425813 
> 
> 
> about the encryption process.
> I know since LibreOffice v3.5 AES-256 (in CBC mode) is using. I using 
> LibreOffice v6.3.
> Is there a official specification on the implementation of encryption 
> and decryption in LibreOffice documents (Which algorithms can be used, 
> what exactly is the procedure, which coding methods are used, how will 
> the data be processed (padding))? Where I can find this sepcification?

i'm not aware of anything specific to LO, just the file format 
specifications from OASIS and Microsoft.

in addition to ODF encryption, which is not ideal but at least somewhat 
competent, there are various legacy hashing & encryption schemes 
supported for interoperability with legacy formats, such as binary MSO 
files; these can be arbitrarily bad ("XOR encryption").

iirc Microsoft Office's non-standard OOXML encryption is also 
implemented, but i don't know anything about that... presumably this is 
well designed, seeing as it's the newest design.

oh, one thing that's odd that comes to mind about ODF encryption is 
there's some addChaffWhenEncryptedStorage function to add XML comments 
with random characters; i forgot what problem that was supposed to solve.