The rise of quantum computing has sparked concerns about the security of legacy blockchains, with Google warning that a powerful enough machine could exploit them with less effort than previously thought. For XRP holders, experts offer a more nuanced view: the architecture of XRP may provide 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 break down the details step by step. The threat to blockchains lies in their fundamental cryptographic features, including private keys used to sign and execute transactions.

A public key, derived from the private key, is used to generate a wallet address that can be shared with others to receive funds. However, a sufficiently powerful quantum computer running 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 when a transaction is sent, making account activity a factor in quantum vulnerability, rather than the balance or how long an address has been held. An audit of the XRP Ledger found that around 300,000 accounts holding 2.4 billion XRP have never sent funds and thus have never exposed their public keys, making them quantum-safe by default.

In contrast, dormant 'whale' accounts that have transacted in the past and exposed their public keys are at risk, with two such accounts found to hold 21 million XRP, or 0.03% of the circulating supply. The XRP Ledger's feature of signing key rotation allows users to swap their signing key without moving funds, reducing vulnerability. However, this feature is not foolproof, especially for long-dormant accounts that may have lost keys or are no longer actively managed. Another defense against quantum risk is the 'escrow feature,' which locks funds with a time lock, making them safe not because of cryptography, but due to logic.

While the time lock protects the funds, the account that locked them can still carry quantum risks. In comparison, the quantum threat to Bitcoin appears more significant due to its larger scale and the lack of a key rotation feature. A significant portion of early bitcoin was mined using a format that exposed public keys directly, including Satoshi Nakamoto's 1 million BTC, which has never moved.

Google estimates that about 6.9 million BTC are vulnerable, equating to nearly 35% of bitcoin's circulating supply. Bitcoin holders face a structural problem in protecting their funds, as moving them to a new address exposes the public key of the old address, making it vulnerable to quantum attack during the transaction process.

Although this risk is still theoretical, it highlights the relative structural vulnerability of bitcoin holders compared to XRP holders.