  In the resource-constrained world of the digital landscape, lightweight
cryptography plays a critical role in safeguarding information and ensuring the
security of various systems, devices, and communication channels. Its efficient
and resource-friendly nature makes it the ideal solution for applications where
computational power is limited. In response to the growing need for
platform-specific implementations, NIST issued a call for standardization of
Lightweight cryptography algorithms in 2018. Ascon emerged as the winner of
this competition. NIST initially established general evaluation criteria for a
standard lightweight scheme including security strength, mitigation against
side-channel and fault-injection attacks, and implementation efficiency. To
verify the security claims, evaluating the individual components used in any
cryptographic algorithm is a crucial step. The quality of a substitution box
(S-box) significantly impacts the overall security of a cryptographic
primitive. This paper analyzes the S-boxes of six finalists in the NIST
Lightweight Cryptography (LWC) standardization process. We evaluate them based
on well-established cryptographic properties. Our analysis explores how these
properties influence the S-boxes' resistance against known cryptanalytic
attacks and potential implementation-specific vulnerabilities, thus reflecting
on their compliance with NIST's security requirements.
