I need digital signature scheme with following rules:
- Signature is "anonymous" which means it doesn't expose author identity (See papers in this answer. Anonymous RSA version or Boneh-Boyen algorithm satisfy this clause).
- Author can create some anonymous signed message and then create another anonymous signed messages "related" to any previous signed message.
- "Relation" means third party can make sure this second message have same author as its "related message".
- Alice write message and sign it. For example it is volume of the book. Bob cannot determine this message belong to Alice even he has Alice's public key.
- Alice write another message, which are for example second volume of her book and sign it. Bob also cannot determine this message belongs to Alice, but he can make sure this message have same author.
- Alice write third message and sign it. This message is not related to previous, so Bob cannot determine nor author neither relationship with previous messages.