Blockchain-Envisioned Post-Quantum Secure Sanitizable Signature for Audit Logs Management

Audit logs are one of the most important tools for transparently tracking system events and maintaining continuous oversight in corporate organizations and enterprise business systems. There are many cases where the audit logs contain sensitive data, or the audit logs are enormous. In these situations, dealing with a subset of the data is more practical than the entire data set. To provide a secure solution to handle these issues, a sanitizable signature scheme (SSS) is a viable cryptographic primitive. Herein, we first present the \textit{first} post-quantum secure multivariate-based SSS, namely ${\sf Mul-SAN}$. Our proposed design provides unforgeability, privacy, immutability, signer accountability, and sanitizer accountability under the assumption that the $MQ$ problem is NP-hard. ${\sf Mul-SAN}$ is very efficient and only requires computing field multiplications and additions over a finite field for its implementation. ${\sf Mul-SAN}$ presents itself as a practical method to partially delegate control of the authenticated data in avenues like the healthcare industry and government organizations. We also explore using Blockchain to provide a tamper-proof and robust audit log mechanism.