I'm looking for a method for a scenario with following requirements:
At least 3 people (A,B,C,...) are in a Network where they can broadcast messages to everyone but not communicate with a specific person, so that they can't get answers to their broadcasts.
Every member has a public address "Apub, Bpub, .." (max ~100 bytes) which was derived from a private secret "Apriv, Bpriv, .."
- A signs a message with Bpub and broadcasts it to the network.
- B broadcasts a request (based on his Bpriv/Bpub without revealing these 2 keys) to validate, that the message from A belongs to him
Is C able to validate the request from B, without knowing Bpriv/Bpub and therefore not knowing his identity?
A shouldn't be able to proof, that the message was signed for himself without knowing Bpriv.
Are there existing code examples for this, which are free to use and free from patents?