The rising threat of quantum computing has sparked intense discussion, particularly after Google announced that a sufficiently powerful quantum machine could potentially breach traditional blockchain security with less effort than previously thought. For XRP holders, the situation is more nuanced, with experts suggesting that XRP's architecture may offer better protection against quantum attacks than Bitcoin's. XRP operates on the XRP Ledger, an open-source and decentralized blockchain, which is utilized by Ripple for facilitating cross-border transactions.
Let's examine this in more detail. The primary threat to blockchain security from quantum computing lies in its potential to reverse-engineer private keys from public keys, thereby allowing unauthorized access to funds. Typically, a user's public key is exposed when they send a transaction, making their account activity a potential vulnerability, rather than their balance or the duration for which they have held an address.
Recently, a quantum vulnerability audit of the XRP Ledger found that approximately 300,000 accounts, holding around 2.4 billion XRP, have never sent funds and thus have never exposed their public keys to the network, making them quantum-safe by default. However, there are dormant accounts that have previously transacted and exposed their public keys, but these are relatively few, with only two such accounts found, holding about 21 million XRP, which is a mere 0.03% of the circulating supply.
A key feature of the XRP Ledger that mitigates quantum risk is the ability to rotate signing keys without moving funds, a process akin to changing the lock on a house without needing to move. While this feature is available to all users, the challenge arises with long-dormant accounts whose owners may have lost their keys or are no longer active, making these accounts vulnerable.
Mayukha Vadari, a staff software engineer at Ripple, highlighted the escrow feature as another mechanism that can protect against quantum risk. Funds locked in escrow with a time lock are safe because the logic of the time lock prevents withdrawal until a specified time has passed, regardless of cryptographic vulnerabilities. It's worth noting that while the time lock safeguards the funds, the account itself can still carry quantum risks, and an attacker could potentially take control of the account and modify or cancel the escrow. In comparison, the quantum threat to Bitcoin appears more significant for two reasons.
Firstly, a substantial portion of early Bitcoin, including Satoshi Nakamoto's 1 million BTC, was mined using a format that directly exposed public keys, making about 6.9 million BTC vulnerable to quantum attacks, which is nearly 35% of Bitcoin's circulating supply. Secondly, Bitcoin lacks a key rotation feature, forcing holders to move funds to a new address to protect them, but this process temporarily exposes the public key of the old address to potential quantum exploitation. Although the risk is still theoretical, it underscores the relative vulnerability of Bitcoin holders.
It's notable that Bitcoin developers have begun proposing solutions to develop quantum resistance.