2. A method as described in claim 1 further comprising the step of: a) providing verifying means for receiving said enabling information and for decrypting said encrypted information E, said verifying means further comprising memory means for storing preselected decryption keys CD, said preselected keys CD being in one-to-one correspondence with said classes, and still further comprising means responsive to said enabling information for enabling said verifying means to access selected groups of said preselected keys; and wherein, b) said enabling information comprises information defining a group of said preselected keys CD corresponding to said selected groups of classes.
6. A method as described in claim 2 comprising the further step of: a) transmitting request information to a data center, said request information including encrypted information identifying said verifying means and a request for enabling information defining said group of said preselected keys CD corresponding to said selected group of classes: wherein said data center decrypts said encrypted identifying information and responds to send said requested enabling information to said verifying means.