PQC: Lattice-based signatures

The recent discussion highlights the potential integration of a hybrid cryptographic scheme within Bitcoin's development framework, specifically combining BIP340 and Dilithium public keys. This proposed method involves using script commands OP_CHECKSIGVERIFY followed by OP_CHECKDILITHIUMSIG, aiming to enhance security measures. The primary advantage of this system is its preventative nature against independent use of Post-Quantum Cryptography (PQC) CHECKSIG operation, which could be vulnerable due to possible bugs in new schemes or implementations.

A significant consideration with the hybrid scheme is its opt-in feature, which underscores its voluntary adoption rather than being a mandatory update. This flexibility allows for a gradual acceptance and implementation within the community, depending on their readiness and assessment of the technology's reliability and necessity. However, it's important to note that the restrictions imposed for safety reasons today might limit future adaptability and efficiency. As such, there needs to be a mechanism in place to modify or relax these restrictions as the cryptographic landscape evolves and stabilizes over time.