Privacy preserving secret key extraction protocol for multi-authority attribute-based encryption techniques in cloud computing

In the existing privacy-preserving multi-authority attribute-based encryption (MA-ABE) techniques, the users receive their secret keys from multiple authorities, where each authority maintains a different set of user attributes with major control established by a central authority (CA), who manages all the attribute-related activities (causes collision attack). Also, as the secret key is derived from user sensitive attributes, the authorities may collect and analyse the user attributes to recognise a user's identity which leads to compromised key attack and insider attack. In order to solve these issues, we propose a privacy preserving secret key extraction (PPSE) protocol, which stores user attributes in fuzzy attribute set format over hash index. This enables easier extraction of the secret key from outsourced user attributes and it eliminates the need for the involvement of a central authority for user attribute management. We implemented PPSE using Charm crypto (Akinyele et al., 2013) and the experimental results show that our scheme provides higher levels of user access provision with improved security and privacy.