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Door Remote - 26 Sep 2026
The connection to Zcash goes back further than Thursday’s paper. Zerocoin was proposed as a privacy extension to Bitcoin in 2013, the subsequent Zerocash research developed into Zcash, which launched as a separate cryptocurrency in 2016.
Shielded Bitcoin would keep the encrypted transfer data on Bitcoin so users could reconstruct accepted payments from the public record using their wallet keys. Separate viewing keys would allow them to disclose transactions to an accountant or auditor without handing over permission to spend their funds.
Unanswered questionsThe 56-page specification does not explain how ordinary BTC would enter that system or be released when someone wanted to withdraw. The authors reserve those mechanisms for a separate paper using PIPEs, a technique designed to lock a Bitcoin signing key until specified conditions are met. Their claim that users retain control of their funds covers transfers inside the system and explicitly excludes deposits and withdrawals.
Meanwhile, the omissions have drawn criticism from developers and Zcash supporters.
Mert Mumtaz, cofounder of Helius, which provides infrastructure for Solana developers, and a Zcash proponent, described the proposal on X as “a synthetic ledger with significant tradeoffs.”
He pointed to “a trusted setup” and “no fee anonymization,” meaning the Bitcoin wallet paying to publish a private transfer could still be visible. He also criticized the absence of a deposit and withdrawal mechanism, writing that there was “no in-protocol mechanism for getting actual BTC in or out (which means you are holding synthetics).”
Shielded Bitcoin would keep the encrypted transfer data on Bitcoin so users could reconstruct accepted payments from the public record using their wallet keys. Separate viewing keys would allow them to disclose transactions to an accountant or auditor without handing over permission to spend their funds.
Unanswered questionsThe 56-page specification does not explain how ordinary BTC would enter that system or be released when someone wanted to withdraw. The authors reserve those mechanisms for a separate paper using PIPEs, a technique designed to lock a Bitcoin signing key until specified conditions are met. Their claim that users retain control of their funds covers transfers inside the system and explicitly excludes deposits and withdrawals.
Meanwhile, the omissions have drawn criticism from developers and Zcash supporters.
Mert Mumtaz, cofounder of Helius, which provides infrastructure for Solana developers, and a Zcash proponent, described the proposal on X as “a synthetic ledger with significant tradeoffs.”
He pointed to “a trusted setup” and “no fee anonymization,” meaning the Bitcoin wallet paying to publish a private transfer could still be visible. He also criticized the absence of a deposit and withdrawal mechanism, writing that there was “no in-protocol mechanism for getting actual BTC in or out (which means you are holding synthetics).”