Zakura has outlined a wallet-level change intended to protect the privacy of Zcash users who swap through NEAR Intents. Its proposal gives each publicly posted swap address a separate incoming viewing key. If a sufficiently powerful quantum computer were eventually able to recover the key behind one address, the exposure would be limited to payments associated with that swap rather than the wallet's wider receipt history. The design is a proposal for wallet software, not a deployed network-wide fix or evidence of an attack today.

Why a swap address matters

The engineering post describes a specific point of exposure in cross-chain transactions. For a swap from ZEC to another asset, NEAR Intents records a Zcash refund address on NEAR's public chain when the deposit is registered, even if no refund is ultimately needed. A swap into ZEC can similarly publish a recipient address. These addresses may look unrelated, yet ordinary diversified addresses within one Zcash account derive from the same incoming viewing key. Publishing an address creates a durable record that a future attacker could revisit.

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A conventional computer cannot feasibly derive that viewing key from the address under the cryptography described by Zakura. The concern is hypothetical: a sufficiently capable quantum computer using Shor's algorithm could potentially reverse the relevant elliptic-curve operation. Recovering the shared viewing key could then reveal and link payments received by the account, including amounts and memos. The spending key is separate, so this scenario concerns confidentiality rather than a demonstrated ability to take the user's funds.

A separate key without a separate wallet

Zakura's proposed method derives a fresh incoming viewing key for each swap while retaining the account's existing spending authority. That distinction matters because simply creating a new account for every swap would scatter funds across accounts and complicate spending, especially with hardware wallets. Under the proposed design, a hypothetical compromise of one published address would expose only the payments associated with that address. It would not by itself connect the address to the account's other swap addresses or ordinary private receipts, according to Zakura's analysis.

The extra keys create a recovery problem: restoring a wallet from its seed could require checking many keys against historical transactions. Zakura proposes recording a swap-key index in an encrypted change-output memo for outbound swaps. For refunds, a wallet could consult an address-to-transaction index using private information retrieval, so the index server would not learn which address the wallet queried. Inbound ZEC swaps need a different discovery process because they do not leave the same change-output memo. These are proposed implementation details, not guarantees that every wallet will adopt them.

What has not changed

Zakura says software wallets built on its open-source libraries could integrate the one-time-key feature in the coming weeks; hardware-wallet support would depend on firmware. CoinDesk reported the proposal on October 19, describing it as a way to narrow the privacy consequences of a future attack. Neither source says the protection is already active for all NEAR Intents users. Users should not infer from the proposal that existing posted addresses have been retroactively changed.

The broader distinction is between a theoretical future capability and a current exploit. Zakura's post says shielded Zcash transactions remain private against quantum adversaries in many ordinary cases because their addresses are not published on the chain. The swap workflow is different because it places an address on a public ledger. Whether the proposed design delivers the intended protection will depend on implementation, independent review, wallet adoption and the eventual capabilities of quantum computers, whose arrival date remains uncertain.

Sources

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