I tried to setup an automated installation via autoyast and digest authentication. I faced the same problem as with client-certificates.
apache2 error.log: Digest: client used wrong authentication scheme `Basic': /lh/xml/0 ...
yast2-transfer is using libcurl and is using basic auth per default. No possibility to change that.
@Uwe - another point which should be considered with libcurl. Applications like wget decide on type of challenge which encoding scheme to use. May be it could be implemented that way.
Best Regards, Jochen