add function signature registry steps

01_Main_Concepts/07_Best_Practices/00_Function_Signature_Registry.md

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+
+# How to get your function name displayed on the MetaMask Confirm Screen instead of "unknown function"
+
+_MetaMask uses the parity on-chain registry of function signatures to display method names on the confirm screen._
+
+To add your contract's function names to this registry, follow the below steps.
+
+1. Go to the [mainnet parity signature registration contract on etherscan](https://etherscan.io/address/0x44691b39d1a75dc4e0a0346cbb15e310e6ed1e86#writeContract)
+
+2. Connect MetaMask
+
+3. Use etherscan's write contract feature to input the string value (without quotes) to the register function
+
+   for example:
+
+   `getOwners()`
+
+   `execTransaction(address,uint256,bytes,uint8,uint256,uint256,uint256,address,address,bytes)`
+
+4. Press write
+
+5. Approve the transaction through MetaMask (you only pay gas)
+
+
+##### Verify
+
+`web3.sha3('getOwners()') => 0xa0e67e2bdc0a6d8a09ccd6c353c9df590807ad66ff5e6630c4f31a86dfa84821`
+
+take the first 10 characters `0xa0e67e2b`
+and input into **[this demo app](https://jennypollack.github.io/function_signature_registry/) that checks the on-chain registry** (mainnet or rinkeby)
+
+##### Alternate steps using remix.ethereum.org:
+
+Paste the contract code from [bokky's blog post](https://www.bokconsulting.com.au/blog/a-quick-look-at-paritys-signature-registry-contract/) into [remix](remix.ethereum.org)
+
+Set the correct compiler version based on the contract.
+
+Use remix's write functionality to add to the registry.
+
+You can look at the FUNCTIONHASHES section on remix.ethereum.org by loading the signature registry contract, press the Details button on the compile tab.
+
+##### Additional Info
+You can also use the [signature registry](https://rinkeby.etherscan.io/address/0x0c0831fb1ec7442485fb41a033ba188389a990b4) deployed on rinkeby but should note that **MetaMask reads from the mainnet eth-method-registry endpoint, regardless of user's network**
+
+[eth-method-registry](https://github.com/danfinlay/eth-method-registry) is used to lookup methods in MetaMask.
+
+This [stack exchange](https://ethereum.stackexchange.com/questions/59678/metamask-shows-unknown-function-when-calling-method-send-function) answer is a good **tldr**.