Google just released the first "below-threshold" quantum chip, Willow (with 105 qubits for now). It is the first chip capable of real-time error correction, effectively reducing errors while enabling scalable quantum computing. It’s a strong sign that useful, very large quantum computers can indeed be built.
So what does this mean to modern cryptographic systems and cryptocurrency wallets? How much time do we have before they’re no longer safe?
- Elliptic Curve Cryptography (ECC)
Both Ethereum and Bitcoin wallets rely on secp256k1, an elliptic curve cryptographic system. ECC secures funds by leveraging the Elliptic Curve Discrete Logarithm Problem (ECDLP), which is virtually impossible for classical computers to solve.
- Why is ECC Quantum Vulnerable?
Quantum computers, using algorithms like Shor’s algorithm, can solve ECDLP efficiently, breaking ECC entirely. For Ethereum’s 256-bit keys:
Theoretical estimates suggest around 2*n logical qubits are needed for Shor’s algorithm, where n is the key size in bits. For a 256-bit ECC key: 2 × 256 = 512 logical qubits are required.
This makes ECC highly vulnerable as quantum computers approach the required qubit capacity.
- Hash Algorithms (e.g., SHA-256)
Breaking hash algorithms like SHA-256 relies on brute force attacks. Quantum computers cannot break hash functions as efficiently as ECC but can weaken their security:
Using Grover’s algorithm, quantum computers reduce the effective strength of SHA-256 from 256 bits to 128 bits, requiring 2^128 attempts. While this weakens SHA-256, it remains secure for now.
Are Ethereum Wallets at Risk?
With quantum computing advancing quickly, Ethereum wallets that rely on ECC are becoming increasingly vulnerable. To address the potential risk, @VitalikButerin proposed a hard-fork plan earlier this year to save most users' funds during a quantum emergency. https://ethresear.ch/t/how-to-hard-fork-to-save-most-users-funds-in-a-quantum-emergency/18901
- Revert all blocks where large-scale theft is evident.
- Disable EOA-Based Transactions:
- Add a new transaction type, which allows transactions from smart contract wallets
- Add a transaction type or opcode allowing a STARK proof to verify ownership of an address and update the account's validation code for smart contract and user can starts using the smart contract wallet from that point forward.