Using Encryption for Authentication in Large Networks of Computers (Xerox, 1978) 

Jonathan Ledlie April 28, 2000 CS 736 

The Xerox group expands on public and conventional key cryptography to provide algorithms for key distribution and 
authentication.  They identify and provide an adequate solution for one of the 
major external problems of key dissemination (external to the math).  They suggest 
having a hierarchy of key servers, which function like name servers, allowing each 
to be in charge of its subdomain.  One main advantage of their hierarchy is that if one 
machine is compromised, the rest of the system remains safe.  They provide an 
algorithm for authentication so that if I look up someone’s public key I know I’m 
getting the real thing from a trusted key server.  By encrypting the server that I 
want to talk to’s public key with the key server’s private key, I have near-proof 
that the receivers key is correct, because only the key server could have encrypted 
it.  They use caches to eliminate steps from their protocol.  For example, in 
protocol 1 (conventional), caching hews the number of messages from five to three.  
I doubt a solution to this exists, but in their scheme you still have the original key 
dissemination problem.  In order to verify what’s coming from the key server, you 
need its public key to begin with.