Overview
- The 56-page Shielded Bitcoin specification from [alloc] init, published on Sept. 24, 2026, describes a metaprotocol that stores value as encrypted notes and uses nullifiers and ZK proofs to prevent double spends.
- The system puts privacy logic above Bitcoin by embedding protocol data in normal transactions and relying on independent indexers to replay blocks and rebuild the private note state rather than having nodes validate proofs.
- Key deployment choices in the draft raise practical risks: the reference profile reports roughly 330 TB of current storage and replay cost with a target of ~100 GB, and the paper publishes transfers in OP_RETURN blobs that depend on Bitcoin Core v30 relay defaults.
- Cryptography and trust questions remain unresolved because the draft uses Groth16 proofs that require a trusted setup and defers trustless peg-in/peg-out mechanics to a forthcoming paper that will build on PIPEs v2 witness-encryption work.
- Despite strong on-pool confidentiality, observable metadata at deposit and withdrawal points, publication format limits, and optional viewing/compliance features leave linkage and regulatory trade-offs and could pressure standalone privacy coins if the design proves practical.