In constructing our system, our largest technical hurdle is to make it collusion resistant. Prior Attribute-Based Encryption systems achieved collusion resistance when the ABE system authority ``tied'' together different components (representing different attributes) of a user's private key by randomizing the key. However, in our system each component will come from a potentially different authority, where we assume no coordination between such authorities. We create new techniques to tie key components together and prevent collusion attacks between users with different global identifiers.
We prove our system secure using the recent dual system encryption methodology where the security proof works by first converting the challenge ciphertexts and private keys to a semi-functional form and then arguing security. We follow a recent variant of the dual system proof technique due to Lewko and Waters and build our system using bilinear groups of composite order. We prove security under similar static assumptions to the LW paper in the random oracle model.Category / Keywords: Date: received 16 Jun 2010, last revised 26 Dec 2011 Contact author: bwaters at cs utexas edu Available formats: PDF | BibTeX Citation Version: 20111227:055050 (All versions of this report) Discussion forum: Show discussion | Start new discussion