Does anyone have any documentation or support for the following question?

Our IT group is asking this prior to allowing our us to send out  payroll DD stubs using Sage Paperless Office. The PDFs are marked to use the SSN as the password

'For the attachments that are sent in e-mail when the 128-bit encryption box is <checked>,

what type of encryption is used? 
AES or DES"

Also we are on v2019. If this is different in v2021, please post.

Thank you