From the cryptographer's desk: how we chose Sui's post-quantum signature schemes

Sui’s post-quantum transition centers on two NIST-standardized signature schemes: ML-DSA-65 for native account authentication and SLH-DSA-SHA2-128s for high-value vaults. The choice of ML-DSA-65 over the cheaper ML-DSA-44 reflects concerns raised by recent AI-assisted cryptanalysis, which has exposed vulnerabilities in lattice-based schemes previously deemed secure. The decision prioritizes a security margin that accounts for evolving attack methods, despite minimal performance trade-offs.

SLH-DSA-SHA2-128s, a hash-based alternative, is implemented as a Move smart contract rather than natively to mitigate risks associated with lattice assumptions. This approach aligns with hardware wallet preferences and ensures resilience against potential breaks in lattice cryptography. Sui’s existing two-of-two multisig further allows users to combine classical and post-quantum signatures for added security, addressing concerns raised in recent cryptographic debates.

The implementation relies on Sui’s custom Rust wrapper, mysten-mldsa-native-rs, built over the formally verified mldsa-native core from the Linux Foundation’s pq-code-package project. This choice avoids dependency on broader cryptographic libraries, ensuring compatibility with hardware security modules and ultra-low-power devices. Verification costs remain stable, preserving Sui’s high-performance validation network.

Transaction size increases by roughly 50x due to larger signatures, though Sui’s 128 KB limit and programmable transaction blocks mitigate overhead. Public-key caching, planned for future updates, will further reduce redundant data transmission. The transition maintains backward compatibility, with existing recovery phrases and addresses remaining unchanged.