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Munisamy, E. (2023):

Towards efficient Revocable Identity-based Signatures on Lattice Problems

Identity-based Signatures are an important technique for light-weight authentication. A downside of this signature scheme is that when a key is revoked, all signing keys in the entire system have to be reissued by one central authority. There exists some approaches to reducing the effort of reissuing these user keys, among those a method of delegating this computationally expensive task from the central authority to each user. This scheme is called Key Updatable Signature Scheme and was designed and implemented for elliptic curve signatures and will not remain secure in the future quantum age. Lattice-based cryptography is a promising candidate for future IBS schemes due to its worst-case hardness assumption, efficient implementation and so-far quantum resistance.

This thesis provides an introduction to lattice-based cryptography, presenting the mechanisms of various cryptographic primitives. Based on this, the requirements for constructing a KUSS from an elliptic curve IBS scheme are analysed and compared with an existing lattice-based IBS scheme. Although no solution for a fully functional lattice-based IBS is found, a candidate KUSS is sketched and the requirements that remain to be met and proven are concluded.