Researchers Propose Zcash-Style Privacy System for Bitcoin Without a Soft Fork

Shielded Bitcoin proposal brings Zcash-style privacy to BTC using encrypted notes, public nullifiers and zero-knowledge proofs.

Researchers from cryptography firm [[alloc] init] have proposed “Shielded Bitcoin,” a privacy-focused metaprotocol designed to enable private Bitcoin transfers without changing Bitcoin’s consensus rules.

The proposal, developed by Clara Shikhelman, Mikhail Komarov and Aleksei Moskvin, aims to conceal transaction amounts, senders, recipients and links between transfers. BSCN reported the proposal in an X post, highlighting its use of encrypted notes, public nullifiers and zero-knowledge proofs inspired by Zcash.

Shielded Bitcoin Uses Bitcoin as a Data Layer

Shielded Bitcoin is designed to operate on top of Bitcoin rather than modify the network’s underlying consensus mechanism. Under the proposal, Bitcoin would provide transaction ordering and a place to publish encrypted transaction data, while separate software would manage the private system’s state.

The researchers describe the system as a metaprotocol. Shielded transactions would be published through Bitcoin transactions, but Bitcoin itself would not need to understand or enforce the rules governing those private transfers. Instead, a Shielded Bitcoin indexer would process the published data and reconstruct the state of the system.

This approach means the proposal does not require a Bitcoin soft fork or another change to the network’s consensus rules. The researchers instead seek to use existing Bitcoin functionality as the foundation for a separate privacy layer.

Zcash-Inspired Privacy Mechanisms

The architecture draws directly on techniques associated with Zcash’s shielded transactions. Shielded Bitcoin would use encrypted notes to represent private funds, while public nullifiers would indicate that a note had been spent without revealing which specific note was consumed.

Zero-knowledge proofs would provide another layer of verification. According to descriptions of the proposal, the proofs can demonstrate that a transaction is authorized, that the relevant note exists within the system’s history, that the nullifier has been correctly generated and that the transaction does not create additional funds.

The design therefore seeks to keep sensitive transaction information hidden while allowing the separate indexing system to verify that the private ledger remains internally consistent.

Unlike Zcash, however, Shielded Bitcoin would not introduce a separate blockchain or its own consensus mechanism. Bitcoin would remain the underlying publication and ordering layer.

Moving Bitcoin Into and Out Remains Unresolved

One of the main unfinished elements is the mechanism for moving BTC into and out of the proposed shielded system.

The researchers intend to use Bitcoin PIPEs, a cryptographic mechanism previously proposed by [[alloc] init], to construct a peg between regular Bitcoin and Shielded Bitcoin. The mechanism is intended to allow funds to move without relying on an operator, federation or third-party custodian.

However, the researchers have not yet completed the separate work describing this part of the system. A companion paper covering the mechanism for depositing BTC into Shielded Bitcoin and withdrawing it back to the Bitcoin network is still being developed.

The unresolved entry-and-exit mechanism remains a central technical step before the proposed privacy system can provide a complete path for Bitcoin users to move funds between conventional and shielded transactions.

writer: Ethan Collins
Crypto Journalist
Ethan Collins reports on developments across the cryptocurrency and blockchain sector. His work covers market movements, protocol updates, regulatory changes, and emerging trends in digital assets.
He focuses on presenting complex topics in a clear and accessible manner for a broad readership.