[EROS-Arch] Asking a trusted ob about a key.

[Norman Hardy]

Charlie notes <http://www.macslab.com/charlies/NoDC.html> three 
reasons to trust a key because someone that you trust and to whom you 
have presented the key, says that it is OK.

He suggests that these are the only reasons. I think that there are 
many more. See <http://cap-lore.com/CapTheory/KK/TB.html> just one.

Personally I like the idea of dividing my trust between several 
suppliers for the same reason that I dislike monolithic services.

Incidentally this is a case where TBC calls untrusted objects and 
must be wary about extra returns if return keys don't expire on use.