Extending the functionality of blind accumulators: contexts

Blind accumulators collect private keys of eligible entities in a decentralised manner not getting information about the keys. Once the accumulation is complete, an entity processes the resulting accumulator and derives a public key which refers to a private key previously added by this entity. We extend the blind accumulator scheme with the context functionality so that the derived key is bound to a specific context and this key is computationally hard to associate with public keys of other contexts. Blind accumulators with contexts are useful in various e-voting scenarios, for example in revoting. We provide an instantiation of the extended blind accumulator scheme and justify its security.