A New Approach to Threshold Attribute Based Signatures

Inspired by developments in attribute based encryption and signatures, there has recently been a spurt of progress in the direction of threshold attribute based signatures (t-ABS). In this work we propose a novel approach to construct threshold attribute based signatures inspired by ring signatures. Threshold attribute based signatures, defined by a (t, n∗) threshold predicate, ensure that the signer holds atleast t out of a specified set of n∗ attributes to pass the verification. Another way to look at this would be that, the signer has atleast 1 out of the ( n∗ t ) combination of attribute sets. Thus, a new approach to t-ABS would be to let the signer pick some n′ sets of t attributes each, from the ( n∗ t ) possible sets, and prove that (s)he has atleast one of the n′ sets in his/her possession. In this work, we provide a flexible threshold-ABS scheme that realizes this approach. We also prove our scheme to be secure with the help of random oracles.