Securely Outsourcing Decentralized Multi-authority Attribute Based Signature

Attribute based signature (ABS) is a novel primitive of digital signature that allows the signer to endorse a piece of message with a set of certain attributes in order to preserve the privacy of the signer’s identity. There are multiple authorities that issue different secret keys for signer’s various attributes. And a central authority is usually established to manage all these attribute authorities. This brings a huge workload to compute a signature and also a threat to security and privacy if the central authority is compromised. In this paper, we present an outsourced decentralized multi-authority attribute based signature (ODMA-ABS) scheme. Compared with existing multi-authority attribute based signature schemes, the ODMA-ABS scheme achieves a stronger notion of attribute privacy and authority collusion resistance. And the workload to compute a signature is further reduced by utilizing the outsourcing technique, which makes our scheme more practical in reality.