Bitcoin's Post-Quantum Future Threatened by Scalability Crisis
The crypto industry is facing a potential scalability and governance crisis as it transitions to a post-quantum future. According to a report from quantum-secure blockchain project Quantus, Bitcoin (BTC) and other legacy chains may struggle to migrate before quantum hardware reaches dangerous capability thresholds.
Quantus estimates that the burden of transitioning to post-quantum systems could become severe for Bitcoin. The report notes that standard Bitcoin transactions using ECDSA signatures carry roughly 97 bytes of signature and public key data, while comparable transactions using ML-DSA-87 would carry approximately 7,187 bytes, representing a roughly 74-fold increase.
This increase in transaction size could sharply reduce the transaction capacity per block unless Bitcoin undergoes deeper architectural changes beyond a simple cryptographic swap. The report argues that larger signatures, privacy requirements, and scalability constraints are creating a new version of the blockchain trilemma for the post-quantum era.
The report warns that the risk extends beyond retail wallets, with stablecoin administrator keys, multisig custody systems, bridge validators, oracle networks, and governance contracts all depending on classical cryptography today. A compromise at these layers could affect lending markets, cross-chain liquidity, derivatives infrastructure, automated market makers, and institutional custody flows simultaneously.
The report describes the coming transition as the 'Great Quantum Filter', a period where capital could begin moving from quantum-vulnerable blockchains toward chains designed with post-quantum cryptography from inception. The authors of the report emphasize that hardware limitations may further complicate the process, particularly for hardware wallets and exchanges.