are there bitcoin transactions that were valid in 2009 and …
are there bitcoin transactions that were valid in 2009 and 2010 but would not be valid today in the BCH chain?@@gpt-5
Replies
Yes. Several classes of transactions that were consensus-valid on Bitcoin in 2009–2010 would be invalid under today’s Bitcoin Cash (BCH) consensus rules. Examples:
- Mandatory SIGHASH_FORKID (replay protection): After the 2017 UAHF, BCH requires signatures to use the fork-ID digest (bit 0x40 set). Legacy signatures from 2009/2010 (e.g., plain SIGHASH_ALL=0x01) would be invalid on BCH today.
- Spec: https://documentation.cash/protocol/forks/replay-protected-sighash.html
- Spec mirror: https://github.com/bitcoincashorg/bitcoincash.org/blob/master/spec/replay-protected-sighash.md
- Clean stack rule: Since Nov 2018, script evaluation must leave exactly one item on the stack. Early Bitcoin allowed extra stack items, so scripts that succeed while leaving junk on the stack would now be invalid.
- Upgrade refs: https://documentation.cash/protocol/forks/hf-20181115
- Minimal push/number encoding (MINIMALDATA): Since Nov 2019, non-minimal data pushes or non-minimal numeric encodings are invalid at consensus. Early transactions could use non-minimal encodings.
- Spec: https://documentation.cash/protocol/forks/2019-11-15-minimaldata.html
- Upgrade spec: https://upgradespecs.bitcoincashnode.org/2019-11-15-minimaldata/
- Strict DER signatures (BIP66) and related signature strictness: BCH inherited Bitcoin’s pre-2017 soft-forks, including strict DER encoding. Early transactions sometimes used non-strict encodings that would be invalid now.
- NULLDUMMY for multisig: BCH enforces the dummy element to CHECKMULTISIG be empty; non-empty dummies that were once valid are now invalid.
- Coinbase format (BIP34): Miners must include the block height in the coinbase; a 2009-style coinbase without the height would be invalid today.
- Consensus overview (lists coinbase height and other block-level rules): https://documentation.cash/protocol/blockchain/transaction-validation/block-level-validation-rules
Net: while the old UTXOs could still be spent on BCH using new-style signatures, many 2009–2010 transaction forms (as-written back then) violate today’s BCH consensus rules, so the answer is yes.
BCH is not bitcoin