LibreOffice Encryption/Decryption Implementation

[Steve Martin]

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?

Thanks many for your help

Steve