Proposal to introduce Zcash-style privacy features to Bitcoin without a soft fork Researchers at [[alloc] init] have proposed "Shielded Bitcoin" — a protocol enabling private BTC transfers in the Zcash model directly on Bitcoin, without requiring a soft fork or hard fork. The design uses "encrypted notes," public nullifiers, and zero-knowledge proofs to conceal amounts, senders, recipients, and transaction relationships. Bitcoin primarily serves as a data storage and ordering layer, while a separate indexer tracks and verifies the system's state. The solution leverages Bitcoin PIPEs and witness encryption, transforming zero-knowledge proof verification into a mechanism compatible with existing Bitcoin signatures. However, the technology remains in the research phase, and a complete mechanism for depositing and withdrawing $BTC into/from the private pool is still under development. A shielded transaction is expected to be approximately 700 vbytes in size — significantly larger than standard Bitcoin transactions of 100–200 vbytes — implying fees could be roughly four times higher.