Zcash developers have put forward a quantum-protection proposal in their latest engineering plan, aiming to reduce the privacy risk that could emerge if future quantum computers are able to infer a user’s full payment history from a public refund address. The proposal would assign a separate viewing key to each cross-chain transaction. Zakura said compatible wallets could deploy the feature within weeks.
Privacy exposure tied to NEAR Intents
Zcash is built around privacy: transaction amounts, senders, and recipients are hidden from outside observers. But when users swap ZEC for USDC through NEAR Intents, a cross-chain exchange service, the system must leave a refund address on NEAR’s public blockchain so any remaining ZEC can be returned if the transaction does not complete.
That address uses Zcash’s public-key format and is derived from the wallet’s viewing key through elliptic-curve cryptography. Classical computers cannot reverse that process today. Still, Shor’s algorithm, introduced in 1994, showed that a sufficiently powerful quantum computer could do so. The report said Google last week announced that its Willow quantum chip can already produce core components needed for this type of attack, leaving what it described as a leap in scale between current capability and the actual cracking of early Bitcoin public keys.
The risk is more complicated in Zcash because one wallet can generate multiple addresses that appear unrelated while often sharing the same viewing key. If an attacker were to pull a refund address from the NEAR chain and break its key, that could let them link together all historical incoming transactions for that account, including amounts and attached private memos.
Zakura’s approach: one transaction, one key
Zakura, the next-generation software driving the Zcash network, proposes a straightforward fix. Every ZEC transaction routed through NEAR Intents would use its own viewing key. An attacker who breaks a single refund address would then see only the payments tied to that one transaction, not the user’s broader financial trail.
Under the design, the spending key would remain in the user’s main wallet, so the proposal does not change custody of funds. The report described the structure as a form of damage control: even if a quantum attack were to happen, the impact would be contained to a single transaction.
How Zakura handles hundreds of keys
The design creates a practical problem. A user who has made hundreds of cross-chain swaps could end up with hundreds of viewing keys. In a wallet recovery scenario, that would theoretically require scanning the entire Zcash chain with each key, creating a major performance burden.
To solve that, Zakura uses private information retrieval, or PIR. A wallet can query a database to find where refund outputs landed, while the database does not learn which addresses the wallet searched for. The report described this as a zero-knowledge-style query method that preserves wallet privacy and avoids the cost of full-chain scanning.
Wallet rollout timeline
Zakura said software wallets built on its open-source libraries, including Vizor, could support the feature within the coming weeks. Hardware wallets would need firmware updates before they can add the same functionality.
According to the report, that timeline is earlier than the Zcash development team’s target set at the start of this month to complete quantum-resistant payments by January this year.
From theory to implementation
No quantum computer has yet been shown to break an elliptic-curve key in practice. Even so, the report said developers around the world are moving into defensive work at unusual speed. In that framing, Zcash’s latest move marks another concrete attempt by the crypto industry to prepare before quantum-era threats become real.
The article pointed to two broader implications. First, it said the privacy-coin sector’s response to quantum risk is moving out of academic discussion and into engineering deployment, contrasting that with what it described as a wait-and-see stance in the Bitcoin community. Second, it argued that privacy weaknesses in cross-chain services have often been overlooked, and that the NEAR Intents case is a reminder that bridges and swap systems may be among the more fragile parts of the broader blockchain stack.
For Zcash users, the upgrade is not expected to materially change the short-term user experience. Over a longer horizon, though, the proposal serves as a renewed statement of the network’s privacy goals.