37 lines
1.5 KiB
Markdown
37 lines
1.5 KiB
Markdown
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<!--
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order: 1
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-->
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# Chain ID
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Learn about the Ethermint chain-id format {synopsis}
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## The Chain Identifier
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Every chain must have a unique identifier or `chain-id`. Tendermint requires each application to
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define its own `chain-id` in the [genesis.json fields](https://docs.tendermint.com/master/spec/core/genesis.html#genesis-fields). However, in order to comply with both EIP155 and Cosmos standard for chain upgrades, Ethermint-compatible chains must implement a special structure for their chain identifiers.
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## Structure
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The Ethermint Chain ID contains 3 main components
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- **Identifier**: Unstructured string that defines the name of the application.
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- **EIP155 Number**: Immutable [EIP155](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-155.md) `CHAIN_ID` that defines the replay attack protection number.
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- **Version Number**: Is the version number (always positive) that the chain is currently running.
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This number **MUST** be incremented every time the chain is upgraded or forked in order to avoid network or consensus errors.
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### Format
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The format for specifying and Ethermint compatible chain-id in genesis is the following:
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```bash
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{identifier}_{EIP155}-{version}
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```
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The following table provides an example where the second row corresponds to an upgrade from the first one:
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| ChainID | Identifier | EIP155 Number | Version Number |
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|--------------------|------------|---------------|----------------|
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| `ethermint_9000-1` | ethermint | 9000 | 1 |
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| `ethermint_9000-2` | ethermint | 9000 | 2 |
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