Post-quantum Key Escrow for Supervised Secret Data Sharing on Consortium Blockchain

Xiaowen Cai, Wenjing Cheng, Minghui Zhang, Chen Qian, Zhengwei Ren, Shiwei Xu, Jianying Zhou

Abstract: Consortium blockchain has been widely used in different management scenarios (i.e., digital finance), where normal members want to keep their on-chain data private while supervision peers want to reveal the on-chain private data under certain circumstances like financial regulation and judicial forensics, and key escrow is an idea to solve the problem. Since current key escrow schemes heavily rely on traditional asymmetric encryption and decryption algorithms that are vulnerable to attacks from quantum computers, we design and implement the first post-quantum (PQ) key escrow system for consortium blockchains (i.e., PQ-KES4Chain), which is integrated with all the PQ public-key encryption/KEM candidate algorithms in the current round of NIST call for national standard. Furthermore, we provide chaincodes, related APIs together with client codes for further development. And we perform a detailed security analysis on the system design and a full evaluation on the performance of PQ-KES4Chain including the time of chaincodes execution and the on-chain storage space. We further discuss the implications of our findings, which could be helpful for the developers of PQ KEM algorithms and applications.