Nope, man. They are not encrypted.
Just now I enabled logs in SM19 and downloaded a couple of AUD-files from Application Server to my PC. That is how they look like:
2AUJ20190502225613000730800000D0hostname1 SAPUSER1 SM19 SAPMSM19 10021 hostname1 2AUE20190502225613000730800000D0hostname1 SAPUSER1 SM19 SAPMSM19 1002 hostname1 2AUI20190502225613000730800000D0hostname1 SAPUSER1 SM19 SAPMSM19 10021 hostname1 2AUI20190502225613000730800000D0hostname1 SAPUSER1 SM19 SAPMSM19 10022 hostname1 2AUE20190502225613000730800000D0hostname1 SAPUSER1 SM19 SAPMSM19 1002 hostname1 2AUI20190502225613000730800000D0hostname1 SAPUSER1 SM19 SAPMSM19 10021 hostname1 2AUE20190502225613000730800000D0hostname1 SAPUSER1 SM19 SAPMSM19 1002 hostname1 2AUI20190502225613000730800000D0hostname1 SAPUSER1 SM19 SAPMSM19 10022
The format is following:
<date><hostname> <sap_user> <runned_tcode> <some_techcode>
Yes, formatting is a bit weird, without line breaks, but is is a matter of taste.
So they are plain-text and perfectly parsable.