Starknet completes quantum-resistant mainnet test, fixing 2 of 5 risk points

Starknet completed the first quantum-resistant signature transfer on mainnet Aug. 7, a milestone that positions the Ethereum layer-2 as a security leader while exposing five cryptographic weak points across blockchain infrastructure.

The test follows a technical breakdown from StarkWare, the company behind Starknet, which identified five migration surfaces where quantum computers could eventually break blockchain cryptography — keys and accounts, applications and inputs, proving systems, consensus and cross-chain trust, and network transport encryption.

Starknet already addresses two of the five surfaces. Its proof system relies on hash-based STARKs rather than elliptic-curve math, carrying no known quantum weakness, and its programmable accounts let users upgrade signature schemes without a network-wide hard fork. Post-quantum wallets built by Open Zeppelin are already running on its mainnet. The remaining exposure sits in data availability, which Starknet inherits from Ethereum as a layer-2.

The milestone pressures other networks to follow. Sui announced plans to integrate NIST-approved post-quantum signatures — ML-DSA-65 for standard accounts and SLH-DSA-SHA2-128s for Move smart contracts — while Bitcoin faces the hardest path, with millions of coins sitting in exposed addresses and no built-in mechanism to upgrade the accounts behind them.

Shor's Algorithm and the Three Cryptographic Fronts

The core threat comes down to Shor's algorithm. Run on a sufficiently powerful quantum computer, it can work backward from a public key to recover the private key behind it — something classical computers cannot do in any practical timeframe. That single capability turns quantum computing from a theoretical concern into a specific vulnerability for the elliptic-curve signatures (ECDSA) that authorize nearly every blockchain transaction.

Three categories of cryptography carry the exposure, and a quantum computer treats each differently. Signatures prove a transaction belongs to a wallet owner; Shor's algorithm can derive the private key from a public one and sign as that user. Encryption keeps data private in transit, and the same algorithm breaks it too — meaning traffic recorded today could be decrypted years later once the hardware catches up. Hashing, the one-way fingerprints behind proofs and addresses, is mostly touched by a weaker algorithm called Grover's, which speeds up guessing but rarely poses a real threat.

Standardized fixes already exist. For signatures, the recommended path is a post-quantum scheme such as ML-DSA, SLH-DSA, or the proposed Falcon-512. For encryption, the standardized replacement is ML-KEM, formalized under FIPS 203. Hashing needs no new math at all — a sufficiently large hash built on SHA-256 or SHA-3 already stays secure against quantum attack.

Harvest Now, Decrypt Later

The "harvest now, decrypt later" threat compounds the urgency. "Right now all your data is being harvested. Public keys are being saved and put aside by whatever nefarious actors, and they're getting prepared for when the quantum computer comes available," Jerry Lagace, chief operating officer at Krown Technologies, told TheStreet Roundtable. Krown is the blockchain firm behind Qastle, which Lagace called the first truly quantum-secured hot wallet.

For long-lived assets, the exposure begins the moment data is collected, not the day it's decrypted. A Bitcoin address whose public key is exposed today and still holds coins in a decade has, in a sense, already been attacked. Bitcoin currently has no built-in way to upgrade the accounts behind its addresses, leaving only a new quantum-safe address type or an eventual freeze of unmoved funds as realistic paths forward.

No chain can currently claim to be fully quantum-safe, because vulnerable signature and proof schemes remain in active use almost everywhere. The more useful question for developers and users isn't whether a network is "quantum-safe" in the abstract, but how much of its infrastructure already runs on durable hashes versus how much still depends on math a future quantum computer could break — and whether that remaining math can be swapped out without freezing anyone's funds in the process.

This article is for informational purposes only and does not constitute investment advice.