BNB Chain Maps Out Post-Quantum Cryptography Migration Path for BNB Smart Chain

TLDR:

• BSC transaction signatures shift from ECDSA to ML-DSA-44, growing from 65 bytes to 2,420 bytes per transaction.
• pqSTARK aggregation compresses six validator signatures into 340 bytes, achieving a near 43:1 compression ratio.
• Native transfer throughput drops by 40% and gas throughput falls 50% due to larger post-quantum block sizes.
• Median finality holds steady at two slots, while P99 latency rises to 11 slots from cross-region block propagation delays.

Post-quantum cryptography is gaining attention as blockchain networks prepare for long-term security risks. BNB Chain recently published a technical report outlining a migration path for the BNB Smart Chain (BSC).

The report covers quantum-resistant transaction signatures, consensus vote upgrades, and key performance trade-offs.

Researchers found that data size growth, not consensus changes, remains the central challenge for any future production deployment.

Migration Targets Transaction Signatures and Consensus Votes

BNB Chain’s report focuses on two critical layers of BSC’s cryptographic architecture. Transaction signatures currently rely on ECDSA (secp256k1), which is vulnerable to Shor’s algorithm on quantum computers. The proposed migration replaces this with ML-DSA-44, standardized under NIST FIPS 204 in August 2024.

ML-DSA-44 belongs to the lattice-based signature family, built on the Module Learning With Errors problem. It offers NIST Level 2 security, roughly equivalent to AES-128. Researchers chose it over higher variants because signature size directly drives onchain costs.

The consensus layer currently uses BLS12-381 signature aggregation. The report proposes replacing this with pqSTARK aggregation.

Six validator signatures totaling 14.5 KB compress into a single ~340-byte proof, achieving roughly a 43:1 compression ratio.

BNB Chain noted on X: “The biggest challenge wasn’t consensus. It was the increase in transaction and block sizes once quantum-resistant signatures were introduced.”

Throughput Drops While Finality Stays Stable at Median

Test results show a clear performance cost from the larger signature sizes. Native transfer throughput dropped by about 40%, and gas throughput fell by roughly 50% under cross-region conditions. Block size grew from approximately 130 KB to around 2 MB at 2,000 TPS.

The block byte budget became the binding constraint before gas limits were reached. This is because ML-DSA-44 signatures measure 2,420 bytes, compared to just 65 bytes for the current ECDSA signatures. Public keys also grew from 64 bytes to 1,312 bytes per transaction.

Mixed workloads showed smaller drops, around 35% for TPS and 22% for gas throughput. Contract transactions carry higher gas-per-byte, which reduces the relative weight of larger signatures in those cases.

Median finality remained stable at two slots across all test scenarios. The P99 finality latency rose to 11 slots under cross-region PQ conditions, driven entirely by block propagation delays over wider network links, not by any issue within the consensus protocol itself.

Address formats remain unchanged at 20 bytes, derived from the ML-DSA-44 public key through keccak-256. No updates are needed to existing wallets, SDKs, or RPCs. P2P handshakes and KZG commitments remain out of scope for this phase of research.

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