Researchers Propose Zcash-Style 'Shielded' Privacy for Bitcoin Without Changing Its Rules
Key Takeaways
- •A 'Shielded Bitcoin' paper by three researchers at [alloc] init proposes Zcash-style encrypted payments for bitcoin while leaving the network's validation rules unchanged.
- •Under the design, funds would be held in encrypted notes, and spending one would publish a marker plus proofs of ownership and conservation while hiding amounts, sender, and recipient.
- •Unlike Zcash, whose blockchain checks the proofs itself, Shielded Bitcoin would leave verification to external software, meaning a Bitcoin confirmation alone would not prove a private transfer's validity.
- •Zcash's shielded pools held about 4.9 million ZEC worth roughly $7.8 billion, and the network logged around 63,000 shielded transactions last week, its busiest private-transfer week since 2022.
- •ZEC gained more than 2,300% over the past year and traded above $1,600, while Ethereum is reviewing a separate proposal for a shared private pool covering ether and other tokens.
Researchers have proposed a way to make bitcoin payments more private without altering the network's rules, as privacy-focused cryptocurrencies led by Zcash draw renewed investor interest.
The "Shielded Bitcoin" paper, published Thursday by Clara Shikhelman, Mikhail Komarov and Aleksei Moskvin of cryptography firm [alloc] init, borrows the encrypted payment design used by Zcash. As published, the work is a research design rather than a live feature, one that would operate alongside bitcoin as it exists today without changes to how the network validates payments.
Under the proposed system, bitcoin-denominated value would be held in encrypted records called notes. Spending a note would publish a marker showing it had been used, along with a mathematical proof that the sender owned the funds and had not created new ones. The amount, sender and recipient would remain hidden.
A key difference lies in verification: Zcash's blockchain checks those proofs itself, while Shielded Bitcoin would publish the transfer data on Bitcoin and leave the checks to separate software that anyone could run. A Bitcoin transaction could therefore be confirmed while the private payment recorded inside it failed Shielded Bitcoin's checks. In practice, that means participants would need to run or rely on that separate software to confirm a payment's validity, since a Bitcoin confirmation alone would not show whether the transfer inside it had passed the checks.
Privacy has become a practical concern in recent months as developers work to make cryptocurrencies useful for payroll, business payments and everyday spending. Ordinary bitcoin transactions permanently expose amounts and addresses, and once an address is linked to a company or person, other payments associated with it become easier to follow.
Ethereum is also reviewing a proposal for a shared private pool that would let people transfer ether and other tokens without publicly revealing payment details. Its authors cite payroll, treasury management and donations among the uses poorly served by fully public transactions.
How Zcash works
Zcash lets users choose between transparent payments, whose addresses and amounts are public, and shielded payments that encrypt those details.
Its shielded pools held about 4.9 million $ZEC on Friday, up 14% from July 30, according to CoinDesk calculations using ZecStats data. That represents roughly 29% of issued coins, worth about $7.8 billion following the rally.
Zcash recorded roughly 63,000 shielded transactions last week, its busiest week for private transfers since 2022 and the fourth-highest on record. Reported transfer volume across the network exceeded $23 billion, the largest weekly total since 2021 and the second-highest in its history.
Those metrics have attracted both investor money and attention. By early September, $ZEC had gained more than 2,300% over the preceding year and crossed $1,000. It extended the rally above $1,600 on Wednesday.
