Assuming there are a group of individuals with static ecdsa keypairs, of which the public keys are in a shared database that all of them have access to, how can each participant publish an ephemeral public key and prove that it was made by an individual owning one of the static keys in the database without sharing which key it's associated with & without allowing multiple ephemeral keys to "associate" themselves with a single static keypair?

Is there any construction that can deal with both the association part & the making sure there aren't multiple ephemeral keys per static key?

(Not a homework question, just something I was thinking about while reading over proposals for private look-ahead in proof-of-stake blockchains)

  • 2
    $\begingroup$ Take a look at Ring signatures, which allow you to do exactly what you ask for. The original CryptoNote paper contains the description of a ring signature scheme which is relatively easy to understand. $\endgroup$ – VincBreaker May 5 '19 at 15:25
  • $\begingroup$ @VincBreaker want to just make that an answer so I can accept it and close this question? Ring signatures are exactly what I was looking for. $\endgroup$ – Lev Knoblock Jul 23 '20 at 16:28

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