Zakura, a developer of Zcash full node software, has proposed "one-time" viewing keys designed to prevent a future quantum computer from linking a user's shielded Zcash payments. The fix targets swaps through NEAR Intents, in which a user's shielded address is posted on NEAR's public chain.

The proposal, outlined in an engineering post by Zakura developer Adam Tucker, was announced on Sunday. It requires no network upgrade, according to Zakura — meaning the protection can roll out through wallet software rather than a protocol-wide change. Wallets built on the company's open-source libraries, such as Vizor, will be able to add the feature in the coming weeks, with hardware wallets to follow.

Zakura announced the work on X, describing it as "post-quantum unlinkable swaps for Zcash."

Post-quantum unlinkable swaps for Zcash, no network upgrades required.

— Zakura (@ZakuraZcash) October 18, 2026

Zcash's shielded transactions conceal the sender, recipient and amount. Every shielded account has a single incoming viewing key all of its addresses, which the wallet uses to locate and decrypt payments sent to any of them. A classical computer cannot recover that key from an address. According to the post, however, a sufficiently powerful quantum computer running Shor's algorithm could — and would then be able to see the value and memo of every payment the account has received and tie them together.

"Until Tachyon ships, there is a glaring hole: a single published shielded address lets a quantum attacker link every payment that address's key has ever received," Tucker wrote, referring to the proposed scalability upgrade for Zcash that its developers say would also deliver full post-quantum privacy.

The greatest exposure comes from swaps through NEAR Intents, a cross-chain swap service, according to the post. Each swap out of ZEC writes one of the user's shielded addresses to NEAR's public chain as a refund address, whether or not a refund is ever made. The addresses look different from one another, but they all belong to the same account, meaning an attacker who breaks one would expose all of them. In other words, the data a quantum attacker would need is published in the clear today; only the computing power to exploit it is still in the future.

Roughly $600 million to $700 million had flowed through Zcash's NEAR Intents route by May, Zcash Open Development Lab CEO Josh Swihart said at the time — a volume of swaps that each left a refund address on NEAR's chain.

Zakura's fix derives a separate incoming viewing key for each address that has to be published, while leaving the account's spending key untouched. A quantum attacker who breaks one posted address would learn only about the payments sent to that address, containing the damage from any single break to one address's history rather than the account's entire record.

"If a quantum computer ever breaks a posted swap address, it will not be able to link this to any other transaction," Tucker wrote in a Twitter thread.

To keep the additional keys from slowing down restores from a seed phrase, the wallet looks up NEAR's payouts using private information retrieval, a technique that allows it to query a server without revealing which addresses it is asking about.

Zcash's quantum roadmap

The proposal follows Zakura's plan for quantum-safe transparent addresses earlier this month, which also uses private information retrieval and said post-quantum signature opcodes were expected to arrive in Zcash in January. Swihart said in May that Zcash was aiming for full post-quantum status within 12 to 18 months. The one-time keys slot into that timeline as a near-term, wallet-level measure — narrowing the sharpest current exposure while the deeper protocol work, from January's expected signature opcodes to Tachyon's promised full post-quantum privacy, moves ahead.

Concern about the cryptography that secures crypto wallets is growing. Ethereum Foundation researcher Justin Drake and Ethereum co-founder Vitalik Buterin have both warned that AI could break it before quantum computers do.

Wallets using Zakura's open-source libraries will be able to integrate the one-time keys for software wallets in the coming weeks, and hardware wallets will follow once their firmware supports the feature, the post said. Until a wallet ships the feature, swaps made through it would keep posting refund addresses under the shared incoming viewing key.

ZEC was trading at $1,165 Monday morning, up 3.6% on the day, according to Decrypt data.