Age verification

Andrew Cormack Andrew.Cormack at
Wed Dec 7 16:18:45 GMT 2016

Thanks to the person whose Google-skills (or memory) are better than mine :)

See (from 2010) for Kim Cameron's take on the system I was talking about


> -----Original Message-----
> From: ukcrypto [mailto:ukcrypto-bounces at] On
> Behalf Of Andrew Cormack
> Sent: 05 December 2016 18:01
> To: UK Cryptography Policy Discussion Group
> <ukcrypto at>
> Subject: RE: Age verification
> I'm pretty sure someone years ago produced a card that could be used as
> face-to-face proof of over-18ness and nothing else. Sadly my google skills
> aren’t up to finding it but maybe others can. One (chip) end of the card was
> placed in a reader on the bar, other was held by the individual and checked
> their fingerprint. Reader lights up (probably red/green - since I'm colourblind
> that part wasn’t obvious) and you get, or don't, your drink.
> "All" that was needed to complete that system was a trusted (by the pub)
> issuing process to ensure that only over-18s could link their fingerprint to a
> card with that process also being trusted (by the user) not to record/disclose
> identity.
> Online there are a lot more challenges, most obviously that everyone has to
> have a reader, that that reader has to be trusted even in the hands of
> owners who would like to make it lie, etc. And with either type of system you
> have to know in advance what question you want to ask, and ensure that "I
> forgot the card" gives the right answer. But I suspect the technology is the
> easy bit...
> Andrew
> > -----Original Message-----
> > From: ukcrypto [mailto:ukcrypto-bounces at] On
> > Behalf Of Graham Cobb
> > Sent: 02 December 2016 14:37
> > To: ukcrypto at
> > Subject: Age verification
> >
> > Age verification is back in the news again due to the DE Bill.  I have
> > wondered for a while whether crypto could allow us to create some sort
> > of double-blind age verification system: where the identity (name, date
> > of birth, etc) of the person is hidden from the entity needing
> > verification, and the identity of the resource being accessed is hidden
> > from the entity providing verification.  Ideally, of course, it would be
> > triple blind: third parties such as law enforcement cannot find out what
> > resource was accessed by what person, at least not after the fact (maybe
> > they could with prior notification that a particular person or a
> > particular resource was to be monitored).
> >
> > I had in mind something like:
> >
> > 1. Assume that some entities exist who can provide acceptable age
> > verification (I will use a bank as an example below but it could be any
> > private or state entity).
> >
> > 2. Bank verifies your age.
> >
> > 3. You request them to sign a certificate stating that you are over a
> > specific age (say 18).
> >
> > 4. Bank provides the certificate to you.
> >
> > 5. You pass the certificate to the entity needing the proof (say, a
> > nightclub).
> >
> > 6. Nightclub validates the certificate against the bank's public key
> > (without needing to contact the bank).
> >
> > The hard part would seem to be proving that the certificate relates to
> > the actual person who is presenting it (to a practical level of
> > certainty similar to traditional techniques), without allowing the
> > nightclub to find out who that person is! I assume it would have to be
> > based on some sort of temporary secret which you would have to present
> > along with the certificate.
> >
> > I am sure the naive approach above would not work for various reasons
> > but I wonder what work has been done on this? It seems that proof of age
> > for everything from creating social media accounts, to shopping, to
> > drinking, to accessing porn, to ... is becoming more common and it is
> > essential that we have some way of proving age without disclosing who we
> > are, or what we want the proof for.
> >
> > Graham

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