Certificate-free ad hoc anonymous authentication

There is an increasing demand of ad hoc anonymous authentication (AHAA) to secure communications between ad hoc group members while preserving privacy for the members. The main obstacles in AHAA is that it is difficult to deploy traditional public-key infrastructure (PKI) in this scenario and the end users are usually limited in computation. This paper addresses these obstacles with a pairing-free certificateless ring signature scheme. The scheme does not require a setup procedure and each user can sign on behalf of a group generated in an ad hoc way. The signer does not need any certificate but only a legal signer can generate a valid signature to be validated. The signature verification does not leak any information about the signer’s identity, even if the attacker is computationally unbound. The scheme exploits only traditional efficient modular exponentiations, without relying on time-consuming bilinear map operations. The scheme is shown to be secure in the random oracle model. Therefore, our proposal is practical for ad hoc anonymous authentication.