Shielded Bitcoin Aims to Bring Private Transfers to Bitcoin Without Soft Fork
Researchers at Alloc Init have proposed a system to bring Zcash-style private transfers to Bitcoin without requiring a consensus change to the base protocol. The proposal, called Shielded Bitcoin, would conceal transaction amounts, senders, receivers, and links to previously spent funds using encrypted notes and zero-knowledge proofs.
The researchers drew inspiration from Zcash's architecture, which uses similar techniques to maintain user privacy. Unlike Zcash, however, Shielded Bitcoin would not operate its own blockchain or consensus mechanism.
Separate software called indexers would verify zero-knowledge proofs, check that funds haven't been double-spent, and reconstruct the state of the shielded system. The proposal offers a potential path to stronger privacy for Bitcoin users without requiring changes to the base protocol.
The Shielded Bitcoin design has drawn mixed reactions from developers. Vadim Zavodil criticized the proposal on X, arguing that much of its privacy stack had already been implemented by Zcash. He questioned how much privacy a newly launched system could initially provide, given it would start without the anonymity set Zcash has accumulated over years of use.
Pierre-Luc Dallaire-Demers raised concerns about quantum resistance, stating the construction is 'not quantum resistant at all.' However, Eli Ben-Sasson, co-author of the original Zerocash paper and StarkWare CEO, expressed support for the proposal's direction. He noted that the original intent behind Zerocash was to bring privacy to Bitcoin.