> For the complete documentation index, see [llms.txt](https://docs.bitoftrade.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.bitoftrade.com/for-developers/cross-chain-messaging-protocol/how-it-works/signer-service/event-hash.md).

# Event Hash

`eventHash` is calculated from the `eventId` and `eventArgs`: 

```
eventHash = keccak256(eventId,eventArgs)
```

`eventId` is the event params combined together to create a unique id.

```
eventId = EventName + EventChainId + EventContract + EventTransactionHash
```

where: 

* `EventName` - the name of the event 
* `EventChainId` - chainId of the transaction with invoked event 
* `EventContract` - a contract that invoked the event
* `EventTransactionHash` - hash of the transaction with invoked event

`EventArgs` is the event's arguments. All event arguments will be combined in the same order as they were in the event.

```
eventArgs = eventArg_1 + eventArg_2 + ... 
```

For example, for [this](https://etherscan.io/tx/0xa3b1123b8181f27c30f9cae42340325f0fcecf80c7886045dc159a8b8abd9a63#eventlog) `Transfer` event, `eventHash` will be:

```
message=keccak256(
    "Transfer",
    1,
    "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48",
    "0xa3b1123b8181f27c30f9cae42340325f0fcecf80c7886045dc159a8b8abd9a63",
    "0x974CaA59e49682CdA0AD2bbe82983419A2ECC400",
    "0x59169f3c0e9e3630D0EBa5E5561dC1677D9451F3",
    "1574766820"
    )="0x9d4776df88b0ab9bc77fdd2170fc62ce668886290c49b5306bb003d0a751bdc1"
```