Certificate proposal

[Hal]

Bill Stewart <stewarts at ix.netcom.com> writes:
>This doesn't necessarily eliminate certificates - while you have a signed
>statement from Alice's key that she uses Bank Account X, and a signed statement
>from Alice's key authorizing transfer of $D from Bank Account X to Bank
>Account Y,
>the Bank, or a customer, may refuse to accept the request unless there's 
>a signed statement from the Bank's key that Alice's key uses Account X.
>None of these need Alice's name, or for that matter the Bank's, as long as
>there's
>also a signed attribute statement from the Bank's key that it's a bank, etc. 
>The meaning of the certificates changes a bit, but there's still a certificate
>from the bank binding Alice's Key to Alice's Bank Account.

I can see using keys with attributes in this way, for credentials or as
other forms of authorization.  But what about for communications privacy?
What is the attribute that tells you that using this key will prevent
eavesdropping?

Hal