A Formally Specified Blockchain-assisted Post-quantum Authenticated Key Exchange with Verifiable Smart-contract Registration

Abstract

Over time, the security of traditional public-key infrastructures in blockchain systems and in decentralized applications is threatened by the rise of quantum-enabled adversaries.Due to incomplete protocol specifications, unclear validation semantics, and contradictory experimental reporting, it is challenging to apply lattice-based cryptography, which serves as a foundation for quantum-secure primitives, to blockchain-based AKE frameworks.For decentralized applications that use CRYSTALS-Kyber-768 as a lattice-based Key Encapsulation Mechanism (KEM), this study suggests a formally defined blockchain-enabled post-quantum authenticated key exchange and registration framework.The protocol links a public key registration based on a smart contract with an on-chain Groth16 zk-SNARK proof-of-possession verification, which makes for an efficient and authenticated public key registration that is replay-resistant, protects against key-substitution attacks, and establishes a safe session under a well-established adversarial model.To improve traceability, resolvability, and auditability, the suggested protocol separately identifies cryptographic assumptions, block chain consensus assumptions, smart contract validity semantics, and more.To allow for independent verification of the framework's operation, the complete message flows, contract-level validation rules, and on-chain/off-chain boundaries for interactive protocols are all clearly specified.The experiment was conducted on a private Ethereum Proof-of-Stake test network with 50 validators, a gas block limit of 60,000,000, and a block interval of 12 seconds.A set of tests, each consisting of 30 independent runs, was conducted to produce a total of 30,000 registration transactions for the same workload circumstances.The average end-to-end delay is 24.73 seconds, and the registration process includes an average of 275,555 gas.The actual interval of batch-finalization, which is the period between the first batch submitting a transaction and the last batch's finality confirmation in each round of experiment, was used to determine throughput.The throughput that results from running the experiment within the constraints of the blockchain restrictions is comparable to the theoretical, gas-limited processing speed of around 18. 1 tps.Additionally, the lightweight authenticated key exchange phase, which on the tested network settings, carried out about 41 complete bilateral exchange cycles every second, was also accomplished.The outcomes demonstrate that the post-quantum authenticated key establishment can be realistically incorporated into the blockchain-assisted infrastructure with the reproducible system-level behaviors, while maintaining provable proof-of-possession and preserving structured validation semantics.