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Zcash developers at Zakura plan separate keys for each ZEC swap to guard against future quantum computers
According to CoinDesk, Zcash software team Zakura proposes giving every ZEC swap made through NEAR Intents its own viewing key. If a future quantum computer cracks a public refund address, the exposed payment history would be limited to that one swap, and funds themselves would stay safe.
About 5 min read
What happened
According to CoinDesk, the Zakura team said in a new engineering post that it wants to assign a separate viewing key to every ZEC swap made through NEAR Intents. A viewing key is a secret key a wallet uses to recognize which payments were sent to it. CoinDesk describes Zakura as a newer version of the software that runs the Zcash network.
CoinDesk explains that NEAR Intents is a service that lets users swap tokens between different blockchains. When someone swaps private ZEC for USDC, the service publishes one of the user's private Zcash addresses on NEAR's public chain so it knows where to return any unused ZEC. The address is published once the deposit arrives and stays on the chain even after the swap completes and no refund is needed.
Why quantum computers are a concern
According to CoinDesk, every Zcash address carries a public key derived from the wallet's viewing key. The derivation uses one-way elliptic curve math, similar to how Bitcoin and Ether wallets are protected, so such addresses reveal nothing on today's computers. Ordinary computers cannot run this calculation in reverse, but a sufficiently large quantum computer running Shor's algorithm, published in 1994 and designed for exactly this purpose, could in theory work back from an address to the key.
CoinDesk also notes that a Zcash wallet can generate many addresses that look unrelated but usually share the same viewing key. If an attacker cracked that key from a single public address, they could link every payment the account has received and read the amounts and attached private memos. CoinDesk also reports that Google said last week its Willow quantum chip produced a near-perfect version of one of the components consumed by such an attack.
Zakura's approach
According to CoinDesk, spending funds requires a different key, the spending key, so the funds themselves would remain safe. Zakura's plan gives each swap its own viewing key and keeps the spending key in the user's main account. Even if an attacker later cracks a refund address on NEAR, they would see only payments tied to that one swap.
CoinDesk explains that a wallet that has made hundreds of swaps would hold hundreds of keys, and restoring from backup would require scanning the entire Zcash chain with each one. Zakura's solution is a database that wallets query using private information retrieval, to find where refunds landed, without the database learning which addresses the wallet is asking about.
| Item | Current situation (per CoinDesk) | Zakura proposal (per CoinDesk) |
|---|---|---|
| Viewing key | One key usually shared by multiple addresses | One key per NEAR Intents swap |
| Impact if a key is cracked | Could link all of an account's payments, amounts and memos | Only payments tied to that swap would be visible |
| Spending key | Separate from the viewing key | Stays in the user's main account |
| Backup restore | Not described in the report | One key per swap means scanning the whole chain with each key on restore; Zakura solves this by using private information retrieval to look up where refunds landed |
What it means for ordinary readers
CoinDesk notes that no quantum computer able to crack these keys has been demonstrated. Machines that can may still be years away, and no one has a firm timeline. As CoinDesk describes it, the change is meant to limit the damage if keys are cracked later.
According to CoinDesk, Zakura says wallets built on its open-source libraries, including Vizor, may add the feature in the coming weeks, with hardware wallets following once firmware supports it. CoinDesk reports this would put the fix in place ahead of the January target Zcash developers set earlier this month for quantum-resistant payments. The weeks-long rollout is Zakura's own estimate and has yet to happen.
Frequently asked questions
What is the source of this news?
This article is based on a CoinDesk report, which largely relays an engineering post by the Zakura team. The rollout timeline mentioned is Zakura's own statement.
Are current ZEC swaps at risk of being cracked by quantum computers?
According to CoinDesk, no quantum computer able to crack these keys has been demonstrated yet. Such machines may still be years away, and there is no firm timeline.
Would the spending key be exposed?
According to CoinDesk, spending requires a different key, and Zakura's plan keeps it in the user's main account, so the funds themselves would stay safe.
What is private information retrieval?
According to CoinDesk, it is a technique that lets a wallet query a database without the database learning which addresses were queried. It helps wallets find their refunds.
When will it be available?
According to CoinDesk, Zakura says compatible software wallets may adopt it within weeks, with hardware wallets following once firmware supports it. Actual timing depends on each wallet's announcements.
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