Smart Digital Signatures (SDS): A post-quantum digital signature scheme for distributed ledgers

The upcoming quantum era is believed to be an end for the elliptic curve digital signature algorithm (ECDSA) and other number-theoretic digital signature schemes. Hence, the technologies which incorporate ECDSA would be at risk once quantum computers are available at large scale. Distributed ledger technology is one of the potential victims of powerful quantum computers. Fortunately, post-quantum digital signature schemes are already available. Hash-based digital signatures (HBS) schemes due to their simplicity and efficiency have gained tremendous attention from the research community. However, large size of key and signature are the major drawbacks of HBS schemes. This paper proposes a compact and efficient HBS scheme “Smart Digital Signatures” (SDS), which is closer to an existing popular HBS scheme, XMSS. SDS incorporates a novel one-time signature (OTS) scheme in XMSS, namely SDS-OTS. Furthermore, SDS uses a slightly modified version of the key compression tree as compared to XMSS. We have compared SDS with XMSS-WOTS and XMSS-WOTS⁺. The results reveal a significant reduction in hash tree construction time compared to XMSS, and key and signature sizes compared to WOTS and WOTS⁺. Finally, we have also proposed a model for incorporating SDS into a distributed ledger, with the help of High-Level Petri-nets.