How can I set a different password for the screen lock mechanism?

I'm on Suse 12.3 with KDE 4.10.5. Since I sometimes need to ssh into my machine, I choose a long and strong account password. For boot-up, I use auto-login, since the laptop's bios secures booting both with a fingerprint-scan and a password for the hdd (which I think is good enough - or is it not?)

However, whenever I shortly leave my machine or even suspend it to ram, I need the long password which is annoying (since I need to look it up in my password safe), so I sometimes do not lock it. However, I fear that my kids might try typing around on the keyboard at home, or that office mates might pull a prank at the office. So a simple password with 6 or 8 characters would suffice for the screen lock.