The rise of quantum computing has sparked concerns over the security of legacy blockchains, with Google warning that a powerful enough machine could exploit them with relative ease. For XRP holders, the situation is more nuanced, with experts suggesting that the token's architecture provides greater protection against quantum threats than Bitcoin's.
The XRP Ledger, an open-source decentralized blockchain, is the platform on which XRP operates, and its features may offer a degree of safety against quantum attacks. Let's examine this in more detail.
The primary threat to blockchains from quantum computers is the potential to reverse-engineer private keys from exposed public keys, thereby gaining unauthorized access to funds. Typically, a public key is exposed when a transaction is sent, making the account activity, rather than the balance or the age of the address, the determining factor in quantum vulnerability.
Recently, a quantum vulnerability audit of the XRP Ledger revealed that around 300,000 accounts holding 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, dormant whale accounts that have transacted in the past and exposed their public keys are at risk, with two such accounts identified on the XRP Ledger, holding a combined 21 million XRP, which is approximately 0.03% of the circulating supply.
The XRP Ledger's account-based system and signing key rotation feature allow users to swap their signing key without moving funds, thereby protecting their accounts from potential quantum attacks. This feature, although available to all, is not useful for long-dormant accounts whose owners may have lost their keys or are no longer active. Mayukha Vadari, a staff software engineer at Ripple, highlighted the escrow feature as an additional defense mechanism, where funds locked with a time lock are safe due to logical rather than cryptographic reasons.
While the time lock protects the funds, the account that locked them can still be vulnerable to quantum risks. In comparison, Bitcoin's exposure to quantum threats appears more significant, with a larger portion of its circulating supply at risk due to the use of the P2PK format, which directly exposes public keys. Google estimates that around 6.9 million BTC are vulnerable, accounting for nearly 35% of Bitcoin's circulating supply. Furthermore, Bitcoin's lack of a key rotation feature leaves holders with no option but to move funds to a new address, exposing the old address's public key during the transaction process, making them susceptible to quantum attacks.
Although Bitcoin developers have initiated proposals to develop quantum resistance, the current structural vulnerability of Bitcoin holders remains a concern.