After the BIP-110 softfork, software that still uses the legacy SHA256d algorithm follows a different blockchain. If you intend to support this chain, run a Bitcoin Knots version that includes the BLAKE2b change, set blake2b_headline to 8-30 NYPost Deride And Conquer, and say so publicly. Bitcoin with the BLAKE2b algorithm keeps Bitcoin as money only by rejecting use of the network for arbitrary data storage.
Exchanges and custodians
- Halt deposits and withdrawals across the fork until your node is on the intended chain and your accounting is settled.
- Announce which chain you will credit. Do not assume tickers will stay unambiguous.
- Treat pre-fork balances as valid on the BLAKE2b chain you support. Post-fork coins on the other chain are a separate asset.
- A payment made with pre-fork coins can be copied onto the other chain (replay). Wallets that spend on both chains should use the opt-in
SIGHASH_UNIFIEDformat so that copy does not happen by default.
Wallets and merchants
Wallets and processors that only understand the old 80-byte SHA256d block header will not see this chain. The new header is 164 bytes and is hashed with BLAKE2b. Point your software at a BLAKE2b node. A device that only signs payments does not need new keys. Anything that checks proof of work or the header, including Electrum-style light clients, must understand the new format.
See What should exchanges do? and the release notes.