Genesis upgrade
Genesis is a major update to the BitcoinSV mining client which is used by the majority of miners on the BitcoinSV network.
The upgrade is seen as a return to the original Bitcoin protocol, and includes the removal of all limit based consensus rules, and their replacement with miner configurable settings that give node operators the autonomy needed to set their own limits as they determine are practical.
The full specification is available here.
A short summary of the specification is given here.
Genesis is scheduled to go into effect on or around the 4th of February 2019.
See also:
https://bitcoinsv.io/2020/01/15/changes-for-the-genesis-upgrade/
The four following areas of the protocol and specification contain the changes implemented by the Genesis upgrade.
Block Consensus Rules
These consensus rules apply to blocks that are produced after Genesis activation.
- Block Size - The size of a block in bytes of the serialized form of the block including the block header and all of the transactions confirmed by the block.
- Number of CheckSig Operations per MB of Block Space - The consensus rule that limits the number of checksig operations per megabyte of block space has been removed.
Transaction Consensus Rules
These consensus rules apply to transactions that are confirmed in blocks after Genesis activation.
- Maximum Transaction Size - The size of a transaction is the size in bytes of the serialized form of the transaction. The maximum size of a transaction is 1GB (1,000,000,000 bytes). This limitation is expected to be lifted in the future.
- Maximum Number of CheckSig Operations per Transaction
- nLockTime and nSequence - After Genesis activation, the functionality of the nLockTime field of a transaction and the nSequence fields of transaction inputs revert to their original purpose. The rules defined here only apply to transactions that are confirmed after Genesis activation.
Script Language Rules
Bitcoin Script is the programming language that is used to lock and unlock transaction outputs. This section contains changes to the Script Language Rules. More can be found at: Advanced Bitcoin Scripting
The rules defined here apply to locking and unlocking scripts for transaction outputs that are created after the Genesis activation. The previous rules apply to transaction outputs created prior to Genesis activation.
- OP_RETURN functionality - the functionality of the OP_RETURN operation is being restored. OP_RETURN will cause termination of the script and the validity of the script is determined by the value of the top item on the stack. See OP_RETURN.
- Formal Grammar for Bitcoin Script - A formal grammar has been defined for Bitcoin Script. There are the following features of this formal grammar.
| The complete script consists of two sections, the unlocking script and the locking script. The locking script is included in the transaction output that is being spent, the unlocking script is included in the transaction input that is spending the output. |
| The unlocking script can only contain constants. The requirement is part of Validity of Script Consensus Rule, defined later. |
| A branching operator (OP_IF or OP_NOTIF) must have a matching OP_ENDIF. |
| An OP_ELSE can only be included between a branching operator and OP_ENDIF pair. |
| OP_RETURN may appear at any location in a valid script. The functionality of OP_RETURN has been restored and is defined later in the section OP_RETURN functionality. Grammatically, any bytes after an OP_RETURN that is not in a branch block are not evaluated and there are no grammatical requirements for those bytes. |
| Note that disabled operations are included in this grammar. A disabled operation is grammatically correct but will produce a failure if executed. |
- Validity of Script Consensus Rule - The locking and unlocking scripts for every input of a transaction must be grammatically valid, as defined by the formal grammar above.
- PUSHDATA Only in Unlocking Script Consensus Rule - After Genesis activation, the unlocking scripts used in transaction inputs may only contain PUSHDATA operations, as defined by the formal grammar.
In contrast to all the other updates in this section, this consensus rule is activated for all inputs of transactions that are, or will be, confirmed in a block after Genesis activation, regardless of the height of the UTXO being spent. This rule is a subset of the Validity of Script Consensus Rule defined above but is included separately because the activation conditions are different.
- Sunsetting P2SH, OP_CHECKLOCKTIMEVERIFY, and OP_CHECKSEQUENCEVERIFY - The P2SH capability is being removed by the Genesis upgrade and the presence of a p2sh script template in an output will invalidate a transction. The opocde operations revert to NOPs, which have no effect.
- Disabling Operations Consensus Rule - OP_2MUL, OP_2DIV, OP_VERIF, OP_VERNOTIF . If they are present in un-executed script, the script execution may succeed.
Functionality provided by these consensus rules is now covered by the Stack Memory Usage Consensus Rule.
| Consensus Rule | Description |
| Script Element Size | Limits the maximum size of a script element. |
| Stack Size | Limits the combined number of elements that can be placed on the stack and the altstack. |
| Script Size* | The maximum size of the script |
| Number of Non-Push Operations per Script | Limits the number of non-push operations per script. |
- functionality also covered by the Maximum Transaction Size Consensus Rule.
| Consensus Rule | Description |
| Numeric Value Size | |
| Number of Public Keys per Multisig Consensus Rule | |
| Stack Memory Usage |
Standard Local Policies
Policies are settings that are configured by software operators. These settings are generally required by software implementations.
Policies control which transactions the software will propagate across the P2P network or include in a block. However, policies are not Bitcoin Rules or Consensus Rules and are not used to determine the validity of blocks or the transactions confirmed by the block.
Standard Local Transaction Policies
- Maximum Acceptable Transaction Size Policy
- Transaction Evaluation Timeout
Standard Local Script Language Policies
- Numeric Value Length
- Stack Memory Usage
Standard Local P2P Network Policies
- Propagation of non-Standard Transactions