> > So when you guys talk about ongoing reliance with an issuer, is the > converse case you have in mind that the issuer gives me a long-lived thing, > and then they never need to be heard of again? >
Yes, that is one type of case and probably the most extreme zero-reliance example. There's also a gradient of how much reliance might be needed on the issuer between the two extremes of none-ever and every-token. Perhaps they're long-lived and the issuer has the ability to publish a revocation. Maybe the issuer is just part of a scheduled workflow and not allowed to store state such as payment or PII. That seems like a pretty exotic property compared to how current > authentication systems work. Even in the good old Web PKI, with 2-year > certificates, the issuer had to stay alive to serve OCSP responses or > CRLs. Even driver's licenses and passports have revocation! > Just because it's not the common issuer pattern today doesn't mean it's not useful. For example, proving that you lived in a state or worked for an employer X years ago. Those issuers may no longer support your relationship, but you can still prove (with privacy) that you once had a valid relationship. I'd suggest it only seems exotic because current authentication systems were designed with the limitations of current crypto. In 10 years the best practice could absolutely shift to a single issuance and multi-presentation as the de facto most efficient pattern, even when privacy isn't required. Is the requirement here that the holder needs to be able to generate an > indefinite number of unlinkable presentations from a single issuance > transaction? I'm having trouble imagining how you achieve that along with > other properties, so an intro to the relevant crypto would be helpful. > Yes, and there's a variety of well-studied solutions: https://identity.foundation/bbs-signature/draft-looker-cfrg-bbs-signatures.html https://webcache.googleusercontent.com/search?q=cache:HwNzRk1jR60J:https://misterwip.uk/cl-signatures/ https://eprint.iacr.org/2020/979 https://github.com/Zhiyi-Zhang/PS-Signature-and-EL-PASSO https://github.com/microsoft/Spartan
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