Ordinary computers cannot reverse the complex mathematical operations underpinning modern cryptography, but a sufficiently powerful quantum computer running Shor’s algorithm—published in 1994 specifically for this purpose—could theoretically work backward from a public address to the private key.
This vulnerability poses a significant threat to legacy networks like original Bitcoin, where public keys are permanently exposed on the blockchain. Just last week, Google revealed that its Willow quantum chip achieved a critical milestone by producing near-perfect components necessary for such an attack, marking a step toward a machine powerful enough to execute it.
While large-scale quantum computers capable of breaking encryption remain years away—with no firm timeline for their construction—the cryptographic community is actively racing to develop post-quantum defenses.
One key for every swap
Despite its advanced privacy features, Zcash faces its own unique structural challenge. While a Zcash wallet can generate numerous seemingly unrelated addresses, these addresses typically share a single viewing key.
If an adversary successfully compromises this shared viewing key using a quantum attack, they could link every transaction the account has ever received, exposing the amounts and private memos attached to them.
Fortunately, spending requires a separate key, meaning the funds themselves would remain secure. Zakura’s proposed solution introduces a distinct viewing key for each individual swap while keeping the main spending key securely within the user’s primary account. Under this design, an attacker who eventually cracks a refund address on the NEAR blockchain would only be able to view the payments associated with that specific swap.
This architectural adjustment also resolves a practical bottleneck in the user experience, ensuring that privacy is maintained without compromising the operational efficiency of cross-chain swaps.
