QC can
compromise the security of existing blockchains by breaking the underlying
that secure transactions. This could allow attackers to forge digital signatures, steal digital assets, and manipulate data, but not to "duplicate" the blockchain itself. The vulnerability exists for transactions where the public key is already visible on the blockchain.
How quantum computing threatens blockchain security
- Breaking digital signatures: Quantum computers, using algorithms like Shor's, can solve the mathematical problems that keep public and private keys separate. This would allow an attacker with a powerful enough quantum computer to derive a private key from a public key, enabling them to spend another person's cryptocurrency.
- Compromising hash functions: While not as easily broken as public-key cryptography, quantum algorithms like Grover's can weaken hash functions, potentially leading to data integrity issues.
- Exposing vulnerable funds: The attack is most effective against addresses where the public key has already been published through a past transaction. Funds in addresses where the public key has never been revealed are currently considered safer from this specific type of quantum attack.