Random Numbers Boxes and Cypher Processers

Ok folks, sounds like its time to look into the guts of Telebits and XyZel's and see if we can make cypher-processers of them. Both have real CPU's and DSP's, what more do you want? Hardware devices tend to have barely enough processing power to do the function they were designed for---if there were some power left over, the designers would have used a cheaper and weaker processor. Why would you want to do encryption in your modem instead of on the host cpu that the modem is talking to?