Key Highlights
- Researchers from [[alloc] init] have unveiled a specification for Shielded Bitcoin, a protocol aimed at facilitating private transactions on the Bitcoin network.
- This design incorporates elements from Zcash, such as encrypted notes and zero-knowledge proofs, without necessitating alterations to Bitcoin's consensus mechanisms.
- Details regarding the transfer of BTC into and out of the shielded system are expected to be addressed in a forthcoming document.
A team of researchers at Bitcoin cryptography firm [[alloc] init] has introduced a design for private Bitcoin transactions that conceals the identities of senders, recipients, and transaction amounts while utilizing the existing Bitcoin infrastructure.
The 56-page document, dated September 24, 2026, features contributions from Clara Shikhelman, Mikhail Komarov, and Aleksei Moskvin.
Shikhelman noted on Twitter that significant effort has gone into ensuring the security of Shielded Bitcoin and understanding the information that the protocol may disclose. Komarov referred to it as "ZCash-style privacy on the Bitcoin L1 via PIPEs v2."
ZCash-style privacy on the Bitcoin L1 via PIPEs v2. https://t.co/fhjCBWBhH2
— Misha Komarov (@nemothenoone) September 24, 2026
Scott Odell, COO of [[alloc] init], shared on Twitter that the firm has been developing this concept for some time, emphasizing its potential to enhance Bitcoin's privacy without altering its foundational structure.
In this Shielded Bitcoin framework, value is represented as encrypted "notes," and each transaction is accompanied by a zero-knowledge proof confirming the sender's control over the notes being used and that the inputs and outputs are balanced. A public marker known as a nullifier allows software to prevent double spending without disclosing which note was utilized.
Unlike Zcash, which enforces these rules on its own blockchain, Shielded Bitcoin logs transactions as data on Bitcoin without validating them, while separate software, termed indexers, is responsible for verifying the proofs and reconstructing the shielded state.
The paper also contrasts this approach with Shielded CSV, a 2025 proposal that requires coin holders to manage their own transaction data, which typically cannot be retrieved from the blockchain.
The authors clarify that while timing, fees, and the number of inputs and outputs remain public, "Like Zcash and Monero, Shielded Bitcoin maintains the confidentiality of who paid whom and how much, not the occurrence of a shielded transaction," as stated in the document.
Myriad: When will Bitcoin reach a new all-time high? Click to make your prediction.Mechanisms for Pegging In and Out
The current paper focuses solely on transactions within the shielded system, with details on how BTC enters and exits set to be discussed in a separate paper based on Bitcoin PIPEs v2, earlier research from [[alloc] init] that encrypts Bitcoin signing keys to ensure recovery only with a valid proof.
The existing version employs the Groth16 proof system, which relies on a securely conducted trusted setup ceremony. Each transaction is published using an OP_RETURN output, which amounts to 625 vbytes for a transaction involving two inputs and two outputs, as per the paper's findings.
This method depends on the larger OP_RETURN default established in Bitcoin Core v30, a contentious modification that node operators can revert, so successful relaying relies on a sufficient number of nodes and miners maintaining this setup, according to the authors.
An appendix outlines a potential compliance layer where a "Trust Authority" could certify approved deposits, enabling institutions to verify a note's origin without disclosing the entire transfer graph. Notes lacking such certification would still be valid.
Zcash, which serves as a model for Shielded Bitcoin, is currently traded through regulated funds in both the U.S. and Europe. Grayscale's Zcash ETF started trading on NYSE Arca on August 25, and 21Shares launched Europe's first Zcash exchange-traded product on Euronext Paris and Amsterdam on September 22.
As of September 25, ZEC was valued at $1,592, reflecting a 4% increase over the previous 24 hours, with a weekly peak of $1,658.86, according to data from CoinGecko.