- Zakura proposes separate viewing keys for ZEC swaps through NEAR Intents to limit potential exposure from future quantum attacks.
- The proposal aims to prevent compromised viewing keys from exposing a user’s full Zcash payment history, including amounts and private memos.
- Zakura uses private information retrieval (PIR) to let wallets find refunds without revealing checked addresses to database operators.
Zcash infrastructure developer Zakura has proposed a new wallet feature that would protect users’ transaction privacy against potential future quantum computing attacks. The proposal would assign a separate incoming viewing key to every Zcash (ZEC) swap made through NEAR Intents. This limits the payment history an attacker could expose if they eventually break the cryptography behind a publicly visible address.
The proposal, outlined by Zakura developer Adam Tucker on October 18, targets a specific weakness in cross-chain swaps. NEAR Intents publishes Zcash addresses on its public blockchain so unused funds can be returned if a transaction fails or does not use the full deposit. Those addresses remain visible even when no refund is required.
Zcash’s shielded transactions are designed to hide transaction details, but addresses within a wallet typically share an incoming viewing key. A sufficiently powerful quantum computer running Shor’s algorithm could theoretically recover that key from an exposed address, potentially revealing the amounts and private memos of payments received by the account. No quantum computer capable of carrying out this attack has been demonstrated.
Separate Keys Aim to Limit Potential Exposure
Under Zakura’s proposal, each swap would use its own incoming viewing key while the wallet’s existing spending key remains unchanged. If a future attacker recovered the viewing key associated with one publicly exposed address, the information revealed would be limited to payments linked to that address rather than the wallet’s wider transaction history.
The design also addresses the practical challenge of restoring wallets with many separate keys. Zakura proposes using private information retrieval (PIR), a technique that allows a wallet to locate relevant transactions in a database without revealing to the operator which addresses it is searching.
The change would not require a Zcash network upgrade. Zakura says software wallets built with its open-source libraries, including Vizor, could integrate the feature in the coming weeks. Hardware-wallet support is expected later, once compatible firmware becomes available.
The proposal comes as Zcash developers work toward broader quantum-resistant payment protections, including the planned Tachyon upgrade. However, Zakura’s design remains a proposed wallet-level safeguard, not a network-wide fix already deployed to all users.
The immediate goal is to reduce the amount of private transaction information exposed in a hypothetical future quantum attack. The proposal also allows users to continue spending funds through their existing wallet accounts.
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