Key facts
- Researchers at Alloc Init have proposed Shielded Bitcoin to enable private Bitcoin transactions.
- The system uses encrypted notes and zero-knowledge proofs to hide transaction details.
- It aims to provide privacy without requiring changes to Bitcoin's consensus mechanism.
- Concerns have been raised about the initial anonymity set and quantum resistance of the proposed system.
Researchers at the cryptography firm Alloc Init have published a design for Shielded Bitcoin, a protocol intended to bring Zcash-style private transactions to the Bitcoin network without requiring a soft fork. The proposal, detailed in a 56-page paper dated September 24, 2026, by Clara Shikhelman, Mikhail Komarov, and Aleksei Moskvin, aims to conceal transaction amounts, senders, recipients, and links to previously spent funds through encrypted notes and zero-knowledge proofs. Instead of relying on miners to enforce the privacy protocol, Shielded Bitcoin would use Bitcoin as a neutral publication and ordering layer, with separate indexers verifying the zero-knowledge proofs and managing the shielded system's state.
Concerns have been raised regarding the proposal's anonymity set and quantum resistance. Developer Vadim Zavodil expressed worries about the limited initial anonymity set of a new shielded pool, stating that "Privacy is a function of the crowd. Zcash has a real shielded pool built over years." The researchers acknowledged this limitation, noting that distinctive wallet behavior could still reveal relationships between transfers. Pierre-Luc Dallaire-Demers of Pauli Group also raised concerns about the system's quantum resistance. However, Eli Ben-Sasson, a Zerocash co-author and StarkWare CEO, offered support for the proposal's direction, noting that the original intent of Zerocash was to bring privacy to Bitcoin. The paper covers only transfers within the shielded system, with mechanisms for entering and exiting the system to be detailed in a separate paper.