  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.

Cryptography and Security