Re: AIDs testing and privacy

["Perry E. Metzger" <perry@imsi.com>]

Jim Hart says:
> Challenge: is a crypto protocol possible with the following 
> properties: the doctor writes and signs the prescription,
> and it is not transferable, but the patient doesn't need to
> show ID to the pharmacist to fill the prescription?
> I don't want pharmacists, and whoever else they share the info
> with (insurance companies?  investigators? potential blackmailers?), 
> keeping track of what drugs I take.

It cannot be done. There is no way to prove that you didn't transfer
some cryptographic credential. The only way to know that you are you
is to check your credentials against unforgeable physical
characteristics. All such characteristics can be used to identify you.

On the other hand, I'll point out that a pharmacist has never asked me
for ID.


Perry