Breaking key security: Quantum computers, using Shor's algorithm, could break the public-key cryptography (like ECDSA) that protects crypto wallets, potentially stealing funds.
Private key vulnerability: An attacker with a quantum computer could derive a user's private key from their public key, which is exposed when a transaction occurs.
Threat isn't immediate: The quantum computers needed for such attacks are not yet powerful enough, but the rapid pace of development makes this a growing concern.
No immediate panic: For now, cryptocurrencies remain safe. The current quantum computers are small, error-prone, and lack the required stability.
Hash function reduction: Grover's algorithm could theoretically reduce the effectiveness of hash functions like SHA-256, but its impact is less severe than Shor's.
"Harvest now, decrypt later" is a potential threat in which attackers store encrypted blockchain data now, waiting for a powerful quantum computer to decrypt it later.
Community response: The crypto community is actively working on solutions, including developing new "post-quantum" cryptographic algorithms and protocols.
Quantum-resistant solutions: Projects are investigating quantum-resistant algorithms to protect digital currencies from these emerging threats, ensuring security in the future.
User actions: Until new standards are adopted, users can mitigate risk by not reusing public addresses, which keeps their private key from being exposed.