Kerberos question

[Blaz Primc]

Hi,

reading http://www.bsdlover.cn/?uid-129-action-viewspace-itemid-855 got 
me thinking. In the article the author states:

*One part contains the random key along with the service's name, 
encrypted with the user's long-term key; the other part contains that 
same random key along with the user's name, encrypted with the service's 
long-term key.*

Couldn't an attacker do a known-plain-text attack on the second part of 
the message, because he knows what the "random key" is and by doing that 
acquire the service's long term key...?

I may be missing something, because the description is general, but how 
does Kerberos handle that?

Best regards, Blaž