Bitcoin Cash (BCH) Quantum-Signature Draft Has No Sunday, Nov. 15 Lock-In

A June 10, 2026, proposal for Bitcoin Cash (BCH) outlines post-quantum and hybrid signature verification, but does not give the change a lock-in date. Sunday, Nov. 15, is identified in broader planning for the network’s 2027 protocol upgrade, alongside a separate proposal that shares the same identifier.

Despite the shared CHIP-2026-06 identifier, the proposals describe different changes: one concerns signature verification, while the other proposes a script opcode. Contributor mainnet_pat’s post-quantum draft would use the first byte of a public key to select its signature scheme from a registry. The proposed registry would retain secp256k1 and begin with SPHINCS+ and a hybrid option.

The author described a composite key as one that binds two schemes under one signer with “AND semantics.” Under that design, every component signature would have to verify. The proposed keys could spend ordinary P2PKH outputs, so a new output type would not be required. It describes a possible way to use the proposed signatures with that output format; it does not activate the change on the network or move existing holdings to new keys.

The separate OP_SIGHASH proposal would expose a transaction’s 32-byte signature hash to scripts. A Bitcoin Cash Node merge request opened Aug. 14, 2026, seeks to implement that opcode. 2027 upgrade planning identified Sunday, Nov. 15, 2026, as the lock-in date and listed OP_SIGHASH, Native Elliptic Curve Arithmetic Operations and Faster Blocks among proposals considered realistic to discuss.

Discussion of the post-quantum draft includes debate over which schemes to support. mainnet_pat favored starting with SPHINCS+ and a hybrid option while lattice-based schemes receive further review. Forum participant moonsettler called SPHINCS+ “Way overkill for the migration period.” The 2027 cycle’s stated lock-in date is Sunday, Nov. 15, 2026, but the post-quantum draft itself has no confirmed lock-in or activation date.