Alloc Init Proposes Zcash-Style Privacy for Bitcoin

Alloc Init researchers have proposed Shielded Bitcoin, a metaprotocol that would let users turn regular BTC into private notes, transfer them privately, and eventually turn them back into ordinary Bitcoin, all without changing Bitcoin itself.

What's the Scoop?

• Zcash privacy, but for Bitcoin: Shielded Bitcoin explicitly borrows from Zcash, using encrypted notes and zero-knowledge proofs to hide who sent BTC, who received it, and how much moved. Unlike Zcash, though, it would run as a metaprotocol on Bitcoin rather than a separate blockchain.

• How it works: Deposit 1 BTC and it leaves your normal spendable balance, while you receive a private note representing 1 BTC inside Shielded Bitcoin. Send 0.2 BTC, and that note is replaced with two new encrypted notes: 0.2 BTC for the recipient and 0.8 BTC back to you. Bitcoin records proof that a valid note was spent without revealing which one, breaking the normal public transaction trail.

• More usage, more cover: Notes sit inside a shared global set, so as more users and transactions accumulate, each payment can hide among more possible histories. The paper cautions, though, that timing, unusual amounts, fees, or known counterparties can still narrow that privacy set.

• Still a lot left to build: The paper focuses on transfers once BTC is inside the shielded system. Peg-ins and peg-outs are still unfinished, and the authors explicitly do not claim that entering or exiting will be private or free from transaction linkage.