We can modify our ZK credential to support a limit of N shows as follows. First, let’s have the User select a random key K for a pseudorandom function (PRF), which takes a key and an arbitrary input and outputs a random-looking outputs. We’ll embed this key K into the signed credential. (It’s important that the Issuer does not learn K, so this often requires that the credential be signed using a blind, or partially-blind, signing protocol.3) We’ll now use this key and PRF to generate unique serial numbers, each time we “show” the credential.
5. More on modules
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A second Iranian ship has been reported in waters close to Sri Lanka and has sought emergency permission to dock, a day after a US submarine sank an Iranian frigate killing more than 80 people onboard.
Credit: Leah Stodart / Mashable