Researchers Propose Shielded Bitcoin for Zcash-Style Private Transfers

Researchers at Bitcoin cryptography firm Alloc Init published a 56-page paper on September 24 proposing Shielded Bitcoin, a design for Zcash-style private transfers on the Bitcoin base layer that needs no soft fork or consensus change. The specification, authored by Clara Shikhelman, Mikhail Komarov and Aleksei Moskvin, would hide the sender, recipient and amount of a payment while Bitcoin records and orders the data without validating it.

How the design borrows Zcash’s privacy model

Shielded Bitcoin holds value in encrypted notes, and each transfer carries a zero-knowledge proof that the sender controls the notes being spent and that inputs and outputs balance. A public marker called a nullifier lets software reject double spends without revealing which note was used. Unlike Zcash, which enforces those rules through its own blockchain, the proposal treats Bitcoin as a “neutral publication and ordering layer”: separate software called indexers verifies the proofs and rebuilds the shielded state. “Like Zcash and Monero, Shielded Bitcoin preserves the privacy of who paid whom and how much, not that a shielded transfer happened,” the paper states.

The unfinished parts: deposits, withdrawals and cost