With the Advanced Package Tool(apt) tools it is possible to import 
signatures by installing an rpm only. 
 
To give an example, my signature used to sign rpms, is imported by 
the following 1 liner: 
# apt install --no-checksig --no-postscript rpmkey-suser-rbos  
 
From here on, apt takes care of retrieving the rpm, investigates if the 
signature misses in the gpg signature ring and imports it, when the signature 
misses.  Very convenient for the user. 
 
Especially as many rpmkeys have been collected in one place: 
http://ftp.gwdg.de/pub/linux/misc/apt4rpm/rpmkeys/ 
 
More information about this at: 
http://linux01.gwdg.de/apt4rpm/signing.html#rpmkey 
 
Well the feature request is to extend Yast, YOU and yum with the same 
functionality. 
 
The code that takes care of this functionality in apt is located at: 
/usr/lib/apt/scripts/gpg-import.lua (from the apt rpm).