Constant-Size Hierarchical Identity-Based Signature/Signcryption without Random Oracles

We construct the first constant-size hierarchical identity-based signature (HIBS) without random oracles the signature size is O(λs) bits, where λs is the security parameter, and it is independent of the number of levels in the hierarchy. We observe that an efficient hierarchical identity-based signcryption (HIBSC) scheme without random oracles can be compositioned from our HIBS and Boneh, Boyen, and Goh’s HIBE (hierarchical identity-based encryption)[9]. We further optimize it to a constant-factor efficiency improvement. This is the first constant-size HIBSC without random oracles.