2026년 Zcash는 Quantum Resistant인가요? 비판적 분석

Zcash의 암호화 스택 이해

Zcash는 정교한 다층 암호화 시스템을 사용하며 모든 계층은 사전 양자입니다. 투명한 주소는 양자 컴퓨터에 취약한 Bitcoin와 마찬가지로 secp256k1 ECDSA로 서명됩니다. 각 계층의 양자 취약성을 살펴보겠습니다.

zk-SNARK가 양자 안전이 아닌 이유

많은 사람들은 zk-SNARK가 "고급 암호화"이기 때문에 양자 저항성을 가져야 한다고 가정합니다. 이것은 잘못된 것입니다.

과수원 업그레이드로 이 문제가 해결되지 않음

Zcash의 Orchard 업그레이드(2022년 활성화)에는 몇 가지 개선 사항이 도입되었지만 양자 저항을 추가하지 않았습니다:

"Halo 2는 신뢰할 수 있는 설정 의식을 제거하지만(양자 공격 벡터 제거) 증명 시스템은 여전히 ​​타원 곡선의 이산 로그 문제의 견고성에 의존합니다." — Zcash 재단 기술 문서

"지금 수확하고 나중에 해독" 위협

이것은 Zcash 보유자가 이해하지 못하는 중요한 위협입니다.

귀하가 수행한 모든 보호된 거래는 블록체인에 기록됩니다. 현재 정교한 적(국가, 자금이 풍부한 공격자)이 이 데이터를 수집하고 있을 가능성이 높습니다.

양자 컴퓨터가 가능해지면:

• 모든 묘목/과수원 보기 키는 공개 키에서 파생될 수 있습니다.
• 보호된 거래 금액이 표시됩니다.
• 보내는 사람과 받는 사람의 주소를 연결할 수 있습니다.
• 전체 거래 내역을 재구성할 수 있습니다.
• 귀하의 "비공개" 2023 거래는 2033년까지 공개됩니다

Zcash 대 양자 저항 대안

Zcash Has Already Shipped a Counterfeiting Bug Once

Before discussing what a quantum computer would do to Zcash, it is worth recording what a single misplaced group element already did.

On 1 March 2018, Ariel Gabizon, a cryptographer working on Zcash, found a flaw in the BCTV14 proving system that Zcash's original Sprout protocol used. The construction came from a 2014 academic paper by Ben-Sasson, Chiesa, Tromer and Virza. The proving key contained elements that were not needed to produce a valid proof, and those spare elements could be used to forge one. A forged proof would have allowed an attacker to mint shielded ZEC out of nothing, without limit.

Sit with the second-order consequence, because it is the part that matters. In a shielded pool the supply is hidden by design. Nobody can audit it. The same cryptography that protects a user's privacy would have concealed the counterfeiting completely. There is no balance sheet to check, no address to watch, no anomaly to notice. The flaw and the feature are the same mechanism.

Credit where it is due: fixing quietly and disclosing after deployment was the correct call, and the company did it well. The indictment is not of the people. It is of the assumption underneath the whole field.

That construction sat in published, peer-reviewed academic work for roughly four years. It was read by specialists. It was implemented in production and secured real money. And the hole was still there. Anyone who tells you a zero-knowledge system is safe because the paper was reviewed is describing a process that has already failed once, in exactly this way, on exactly this chain.

This is why the argument for hash-based signatures is not aesthetic. Fewer moving parts, fewer assumptions, fewer places for a spare group element to hide.

What Quantum Actually Breaks in Zcash (Two Different Things)

Most coverage says "quantum breaks Zcash" and stops. The mechanism matters, because there are two of them and they fail in different directions.

One: soundness, which means counterfeiting. Groth16, the proving system Sapling moved to after 2018, has perfect zero-knowledge but only computational soundness. In plain terms: the privacy property holds against an adversary with unlimited computing power, and the integrity property does not. Soundness rests on discrete-logarithm hardness in a pairing group. Break that and you can forge proofs. Forging proofs is counterfeiting. That is the 2018 failure again, except this time there is no patch, because the assumption itself is what failed.

Two: note encryption, which means retroactive privacy loss. Sapling encrypts each note's contents to the recipient using a Diffie-Hellman key agreement on the Jubjub curve. The ciphertexts are on the chain forever. A quantum adversary recovers the shared secret from data already recorded and decrypts the amounts and memos of transactions that happened years earlier. Nothing has to be broken today for this to work. The archive is already being collected.

So the honest summary is not that Zcash is "vulnerable". It is that Zcash is vulnerable twice, on two independent mechanisms, one of which destroys supply integrity and one of which destroys the privacy the chain exists to provide. Orchard's move to Halo 2 removed the trusted setup, which was a genuine improvement, and it did nothing about either of these, because Pallas and Vesta are still elliptic curves.

June 2026: It Happened Again, and This Time Nobody Can Check

On 5 June 2026 Zcash disclosed a critical counterfeiting vulnerability in the Orchard circuit, the component that governs its newest shielded pool. ZEC fell somewhere between 31 and 41 percent depending on which outlet you read. Arthur Hayes announced he had liquidated his entire position.

The mechanics matter, because the summary versions lose the important part. Taylor Hornby, hired in April 2026 to hunt for protocol weaknesses, found it on 29 May 2026 using a custom auditing agent framework paired with a large language model. The flaw was an under-constrained element in the Orchard circuit: roughly two lines of code that allowed arbitrary false inputs to an elliptic-curve multiplication to be accepted as valid. Hornby wrote a working exploit and, in a local regtest environment, generated unlimited undetectable counterfeit ZEC. It was patched on 1–2 June and disclosed on the 5th.

It had been live since Orchard activated in May 2022. Four years.

Read that again. Not "we checked and found nothing". Not "we are confident it was not exploited". There is no way to check. The privacy guarantee that is Zcash's entire product is the same mechanism that makes its supply unauditable. You cannot have one without the other. That is not a bug in the implementation, it is the shape of the design.

The proposed remedy tells you how serious it is: a network upgrade is being explored that would deploy an entirely new shielded pool and enforce turnstile accounting on Orchard coins, specifically so supply integrity becomes verifiable. You do not rebuild the pool and add a supply checkpoint if you are confident about what is already in it.

One more detail, and it is not small. Four years of human review, professional audits and academic attention missed two lines. An AI auditing agent found it in weeks. Take from that what you like about the state of manual cryptographic review.

Twice. Eight Years Apart. The Same Blind Spot.

The 2026 bug is not an isolated incident. It is the second instance of one failure mode.

Same class of failure, same invisibility, eight years apart, through two complete rewrites of the proving system. Sprout was replaced by Sapling because of the first one. Sapling was superseded by Orchard with Halo 2 and no trusted setup, which was supposed to be the mature version. It shipped with a constraint bug that did the same thing.

This is an argument against complexity, not against Zcash engineers, who are good at their jobs. A zk-SNARK circuit is thousands of constraints and soundness requires 하나하나 to be correct. One under-constrained element and the system mints money. There is no partial failure mode.

SPHINCS+ vs zk-SNARKs: The Attack Surfaces Are Not Comparable

Now the quantum question in context. If a two-line constraint error produces unlimited invisible counterfeiting, ask what a broken mathematical assumption produces. That is what Shor's algorithm does to Zcash soundness, and unlike a constraint bug there is no patch for it. You cannot fix "the discrete logarithm problem is now easy" with a network upgrade.

The honest caveat, because this page is not a pitch: hash-based signatures are large. A SPHINCS+ signature is measured in kilobytes where an elliptic-curve signature is measured in bytes, and that is a real cost in bandwidth and block space. We pay it deliberately. The trade is signature size against an attack surface that does not include "somebody mis-specified a constraint" or "the discrete logarithm problem fell".

A SPHINCS+ 시그니처 either verifies or it does not. There is no shielded pool it can silently inflate. That is the whole argument, and it is structural rather than clever.

Inspired by Monero, or Inspired by the Cap Table?

Cryptography is not the only place intent shows up. Launch economics is a cleaner signal, because it is a choice made before anyone is watching.

The Zcash Founders’ Reward directed 20 percent of the first four years of block rewards to founders, investors, employees and advisors. That is public record and it was disclosed openly, so this is not an accusation of anything hidden. It is a statement about what the protocol was optimised for on day one.

Monero took the other road: no premine, no founders’ reward, no investor allocation, CPU mining so ordinary hardware could participate. That is the tradition SynX comes out of. We run a peer-to-peer exchange inside the wallet for the same reason: a chain that needs permission from a centralised exchange to be tradeable has handed that exchange a veto over its own existence.

Zcash 업그레이드가 가능합니까?

포스트퀀텀 zk-SNARK는 활발한 연구 분야이지만 다음과 같은 중요한 과제에 직면해 있습니다.

격자 기반 zk-SNARK

포스트퀀텀 보안을 갖춘 STARK와 유사한 시스템에 대한 연구가 존재하지만 다음과 같습니다.

• 증명 크기는 Groth16보다 10-100배 더 큽니다.
• 검증 시간이 크게 늘어납니다.
• 프로덕션에 바로 사용할 수 있는 구현이 없습니다.
• 완전한 프로토콜 재설계가 필요함

마이그레이션 복잡성

포스트퀀텀 zk-SNARK가 사용 가능해지더라도:

• 기존의 모든 보호 풀은 취약한 상태로 유지됩니다.
• 사용자는 자금을 새 주소로 이전해야 합니다.
• 과거 거래가 영구적으로 노출됩니다.
• 수백만 명의 사용자에 대한 네트워크 업그레이드 조정