However , revoking a key now requires both Alice and Bob to be available , and this creates a problem of reliability .
Now , only Alice and Bob ( in concert ) can revoke a key , and neither Alice nor Bob can revoke keys alone .
Revoking a key now requires both Alice and Bob to be available , and this creates a problem of reliability .
Now , only Alice and Bob ( in concert ) can revoke a key , and neither Alice nor Bob can revoke keys alone .