BNB Smart Chain cuts throughput by 40% in post-quantum cryptography migration tests

BNB Smart Chain has successfully tested a migration to post-quantum cryptography across its transaction and consensus layers, replacing key elliptic-curve cryptographic systems with quantum-resistant alternatives standardized by NIST, according to a recent report.

The upgrade replaced ECDSA transaction signatures with ML-DSA-44, also known as Dilithium2, and substituted BLS12-381 consensus aggregation with pqSTARK proofs. The project did not include peer-to-peer handshake encryption or KZG commitment systems, which remain under consideration for future upgrades.

The work comes as blockchain developers prepare for the long-term possibility that quantum computers could eventually break widely used elliptic-curve cryptography through Shor’s algorithm. BSC said the migration effort was precautionary and not tied to any immediate security threat.

NIST formally standardized ML-DSA under FIPS 204 in August 2024, establishing the first production-ready post-quantum signature framework adopted in the report.

BSC selected ML-DSA-44 from among three standardized parameter sets, citing lower signature size and faster verification speed as the main reasons for the choice. The report said larger variants would create substantially more network overhead while offering limited practical benefit under current threat projections.

The migration sharply increased transaction data size. Signature payloads grew from 65 bytes to roughly 2,420 bytes, while public keys expanded from 64 bytes to 1,312 bytes. Under native transfer workloads of 2,000 transactions per second, block size increased from about 130 KB to approximately 2 MB.

Consensus layer aggregate remains comparatively compact. The report said that six validator signatures totaling around 14.5 KB could be compressed into a single pqSTARK proof of roughly 340 bytes.

Performance testing showed that throughput declined after the migration. Cross-region native transfer workloads dropped from 4,973 TPS in non-post-quantum configurations to 2,997 TPS under the upgraded system. Mixed workloads experienced a smaller decline, falling from 3,695 TPS to 2,406 TPS.

According to the report, larger transaction sizes shifted the network bottleneck from gas limits to bandwidth and propagation latency. Median finality remained unchanged at two slots, although worst-case finality increased in cross-region testing because larger blocks took longer to propagate between validators.

BSC said the findings demonstrate that standardized post-quantum cryptography can already be integrated into blockchain infrastructure, though additional work will be needed to address scaling and networking constraints before broad production deployment.