chaum's patent expiry? (Re: Brands' private credentials)

Jason Holt jason at
Sun May 9 23:03:56 EDT 2004

On Sun, 9 May 2004, Adam Back wrote:

> Anyone have to hand the expiry date on Chaum's patent?  (Think it is
> in patent section of AC for example; perhaps HAC also).

I think it's June 2005.  Actually, now that you mention Chaum, I'll have to
look into blind signatures with the B&F IBE (issuing is just a scalar*point
multiply on a curve).  That could be a way to get CA anonymity for hidden
credentials - just do vanilla cut and choose on blinded pseudonymous
credential strings, then use a client/server protocol with perfect forward
secrecy so he can't listen in.  Hm, I'll have to think it out.


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