The recent surge in interest in quantum computing, fueled by Google's claims that a sufficiently powerful machine could compromise legacy blockchains with less effort than previously thought, has sparked a nuanced discussion among XRP holders. Based on expert opinions, it appears that XRP's architecture may be better equipped to withstand quantum threats than Bitcoin's. XRP operates on the XRP Ledger, an open-source, decentralized blockchain, and is utilized by Ripple, a fintech firm, to facilitate cross-border transactions.
Let's delve into the details, one step at a time. The primary concern is that a powerful quantum computer using Shor's algorithm could potentially reverse-engineer a private key from an exposed public key, allowing an attacker to drain funds.
Typically, a public key is exposed to the network when a transaction is sent, and when funds are received, only the wallet address is visible on-chain. This means that account activity, such as sending funds, makes an account vulnerable to quantum attacks, not the balance or the duration of holding the address. A recent quantum vulnerability audit of the XRP Ledger found that around 300,000 accounts, holding approximately 2.4 billion XRP, have never sent any funds and have only received funds, making them quantum-safe by default.
However, there are dormant whale accounts that have transacted in the past and exposed their public keys, but these accounts have been inactive for at least five years. If a quantum computer were to emerge tomorrow, these whales would be at risk. The audit discovered two such accounts on the XRP Ledger, holding a total of 21 million XRP, which is just 0.03% of the circulating supply.
The XRP Ledger's account-based system and key rotation feature allow users to swap their signing key without moving funds, providing an additional layer of protection. Mayukha Vadari, a staff software engineer at Ripple, highlighted the escrow feature as another defense against quantum risk, as funds locked in escrow with a time lock are safe due to logic rather than cryptography. In contrast, the quantum threat to Bitcoin appears more severe, with a significant portion of early bitcoin mined using a format that exposed public keys directly in the transaction output. Google estimates that around 6.9 million BTC are vulnerable, accounting for nearly 35% of Bitcoin's circulating supply.
Bitcoin holders face a structural problem, as the blockchain lacks a key rotation feature, leaving them with only one option: moving funds to a new address whose public key has never been seen. However, this process exposes the public key of the old address, making it vulnerable to quantum attacks. While Bitcoin developers have initiated proposals to develop quantum resistance, XRP's distinct features may provide a relative advantage in terms of quantum security.