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[juergw]

PiperOrigin-RevId: 999324197

[gemini-code-assist]

Code Review

This pull request introduces support for Post-Quantum Cryptography (PQC) Key Encapsulation Mechanisms (KEM) and Key Derivation Functions (KDF), specifically implementing ML-KEM and HKDF algorithms, alongside utilities for Merkle Tree Certificates (MTC) verification. The review feedback highlights a memory leak in 'native_crypto.cc' where an allocated 'stack' is not freed upon an early return, and missing imports for 'urllib.request' and 'base64' in 'export_to_ag.py' that will cause runtime errors. Additionally, several defensive null checks are recommended in 'MtcUtils' to prevent potential NullPointerExceptions and improve error handling.