Zcash developers are working on a technical fix to protect swap privacy from potential threats posed by future quantum computers. The Zakura team, which develops software for the Zcash network, plans to assign a separate viewing key to every ZEC swap made through NEAR Intents, a service that enables token swaps across different blockchains.
When users swap private ZEC for USDC through NEAR Intents, the service posts one of their private Zcash addresses on NEAR's public chain to track refunds. This address remains visible on the public blockchain even if the swap completes and no refund is needed.
Currently, these addresses reveal no information to conventional computers because each address uses elliptic-curve mathematics similar to what protects Bitcoin and Ether wallets. However, a sufficiently powerful quantum computer running Shor's algorithm could theoretically work backward from the address to recover the viewing key.
Zcash's architecture presents a particular vulnerability: a wallet typically generates many addresses that share a single viewing key. If an attacker were to crack that key from a single published address, they could link every payment the account received and read transaction amounts and attached notes. The proposed fix addresses this by giving each swap its own viewing key while keeping the spending key with the user's main account, limiting exposure to data from only that specific swap.
The team outlined a practical solution for wallets handling multiple swaps. Rather than storing hundreds of keys and rescanning the entire Zcash chain during recovery, Zakura proposes using private information retrieval. This technique allows wallets to query a database about refund locations without revealing which addresses they are checking.
Zakura says compatible software wallets using its open-source libraries, including Vizor, could adopt the feature within weeks. Hardware wallet support would follow once their firmware is updated. This timeline aligns with a January target that Zcash developers previously set for implementing quantum-resistant payments.
