[Cryptography] Anonymous age verification

[Stephan Neuhaus]

On 7/19/26 10:35 PM, Kristian Gjøsteen wrote:
> There is an ongoing EU effort to deploy attribute-based identification (EU Digital Identity Wallet), where a web site can ask the user to show certain attributes.
I was once part of an EU research project to develop privacy-preserving 
attribute-based credentials (P2ABC) into a generally usable "thing", but 
that failed. Part of the reason it failed was that the library we had to 
port over had, oh I don't know, something like a thousand classes and 
hundreds of thousands of lines of code, which made auditing, er, 
challenging. Another part was that the form of the "thing" that we were 
supposed to deliver did not fit well with what the library was doing. A 
third part was that the library had lots of special case code for the 
two use cases in which it had been deployed in production previously.

I will say that one of the things I liked was that the code was 
unencumbered by patents and freely available (blessed by the folks at 
IBM Rüschlikon, who had invented the scheme), and that the principle 
seemed sound.

However, I see tons of problems in practice, mostly to do not with the 
crypto, but with usability. This kind of fine-grained control is nice in 
theory, but, if pushed on to the user, useless in practice because most 
people (and that would include myself in most cases) cannot and don't 
want to decide in detail what attributes to reveal.

Cheers

Stephan