The recent interest in quantum computing, fueled by Google's assertion that a powerful enough machine could compromise legacy blockchains more easily than previously thought, has sparked concern among cryptocurrency holders. For those invested in XRP, experts suggest that its architecture may offer better protection against quantum threats than Bitcoin's. XRP operates on the XRP Ledger, an open-source, decentralized blockchain used by Ripple for cross-border transactions. Let's examine this issue in detail.
The primary threat to blockchains from quantum computing stems from the potential for a powerful quantum computer to use Shor's algorithm to deduce 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 factor in quantum vulnerability, rather than their balance or how long they've held an address.
Recently, a quantum vulnerability audit of the XRP Ledger found that approximately 300,000 accounts, holding about 2.4 billion XRP, have never sent funds and thus have never exposed their public keys, making them quantum-safe by default. However, there are dormant accounts that have transacted in the past, exposing their public keys, but these are relatively few, with only two such accounts found, holding about 21 million XRP, which is just 0.03% of the circulating supply. The XRP Ledger's feature allowing for the rotation of signing keys without moving funds provides an additional layer of protection. This means users can change their account's 'lock' without having to move their funds, keeping them safe from potential quantum attacks.
Mayukha Vadari, a staff software engineer at Ripple, also pointed out the 'escrow feature' as a defense mechanism, where funds locked with a time lock are protected not by cryptography, but by the logic that prevents withdrawal until a specified time has passed. While this protects the funds, the account holding them can still be vulnerable to quantum risks. In comparison, the quantum threat to Bitcoin appears more significant due to the large portion of early bitcoin that was mined using a format that directly exposed public keys.
About 6.9 million BTC are estimated to be vulnerable, which is nearly 35% of Bitcoin's circulating supply, a much larger figure than XRP's 0.03%. Bitcoin holders face a structural problem in protecting their funds, as moving them to a new address temporarily exposes the public key of the old address, making it vulnerable to quantum attacks during the transaction processing time.
Although Bitcoin developers are working on proposals to develop quantum resistance, the current structure leaves holders more vulnerable than those using XRP.