Why would someone want a 20ns block encryption completion on a 1us bus? I was reading the NIST 8114 draft and there's an example of a profile, Sample Profile #2, that shows that 20ns (50MHz) for a block completion for encryption on a CANBUS.  The bus is serial and maxes out at 1us (1MHz).   Is there some standard somewhere that specifies a 20ns completion time for a block cipher?  I cannot figure out, from a hardware standpoint, where that 20ns came from.
The authors of the NIST 8114 draft said that the times were arbitrary for the purpose of generating discussion.  They did, indeed, generate discussion.