Allow Setting of EVM Address by EOA

HIP/hip-1082.md

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+---
+hip: 1082
+title: Allow Setting of EVM Address by EOA
+author: Nana Essilfie-Conduah <@Nana-EC>
+working-group: Richard Bair <@rbair>, Atul Mahamuni <@atul-hedera>, Ty Smith <ty-swirldslabs>,
+Serg Metelin <@sergmetelin>, Ali Nikan <@alinik4n>, Greg Scullard <@gregscullard>
+requested-by: Hedera community
+type: Standards Track
+category: Service
+needs-council-approval: Yes
+status: Draft
+created: 11-18-24
+discussions-to: https://github.com/hashgraph/hedera-improvement-proposal/discussions/1070
+updated: 12-06-24
+replaces: 631
+requires: 583
+---
+
+## Abstract
+
+HIP 583 opened the doors for greater account compatibility with EVM flows by utilizing the account alias to encompass
+the EVM address. However, given the static nature of the alias and concerns of complexity, existing accounts were not
+allowed to update their alias and set one if it was null. This HIP aims to rectify this by allowing EOAs who have no
+alias set to set it to an ECDSA key derived evm address value they own.
+
+This HIP also replaces the need for [HIP 631: Account Virtual Addresses](https://hips.hedera.com/hip/hip-631) as it
+aimed to resolve this issue as well as provide even greater functionality. A form of HIP 631 could be revisited in the
+future but not with the goal of providing address equivalence with the EVM.
+
+## Motivation
+
+The EVM address alias introduced in HIP 583 allowed for ECDSA based accounts to interact with the EVM in the same way
+other EVM chains do. Particularly, functionality like the `ecrecover` that relies on the relationship between key and
+address (pivotal to many DEXs) was unblocked and allowed greater EVM equivalence on the Hedera network.
+However, HIP 583 intentionally provided no solution for accounts with no alias regardless of key type (ED, EC or
+complex keys). Though these accounts were afforded the hedera num account alias (long zero), this format would not
+allow accounts to utilize the `ecrecover` precompile in the expected manner.
+This continued incompatibility has remained and inhibited web3 EVM tooling support.
+
+Providing a solution to this gap is a necessity to make it easy for EVM dApps in the web3 community to come to 
+Hedera without needing to change their smart contracts.
+
+## Rationale
+
+[HIP 631: Account Virtual Addresses](https://hips.hedera.com/hip/hip-631) lays out the challenges faced by accounts
+without an ECDSA derived EVM address that want to interact with the EVM in a way that complies with the Hedera native
+model and the EVM model. However, HIP 631 offered feature rich complexity that may be difficult for DApps, wallets and
+users to follow completely.
+
+Instead of the full HIP 631, an intermediate approach i.e. a HIP 631 Lite (this HIP) could unblock users without an
+EVM address. It would enable accounts to interact with the EVM in a compliant manner regardless of the public key on
+its account.
+
+In a sense the current network already supports the ability to set the evm address, it just requires the logic to be 
+done on account creation. Thus by lifting the limit of not being able to set the alias after account creation, whiles
+still requiring that the current alias be unset this HIP ushers in the ability for those previously blocked accounts to
+interact with the EVM as expected.
+
+### Foundational Concepts
+
+The following are some clarifying concepts to increase clarity around aliases
+- Every account on the network has 1 or 2 evm addresses. Either only the Hedera num alias (long zero) or the Hedera num
+    alias (long zero) and an EVM address alias (standard ECDSA derived EVM address).
+- When a user interacts with the EVM the network will utilize the ECDSA derived EVM address alias on an account if
+    present. If not it will utilize the long zero.
+- Accounts with an ECDSA derived EVM address are fully compatible with expectations of contracts that utilize the
+    ecrecover precompile.
+- Accounts without an ECDSA derived EVM address alias will not match the expectation of the ecrecover precompile
+    calculations. This has effects on certain DApp behaviour.
+- Smart contracts can and do cache the evm address of an account and often use it to assign attributes such as access
+    and ownership. As a result it was important to maintain a static alias to avoid unintended differences in
+    expectation
+- Account key rotation has no impact on the evm address utilized when an account interacts with the EVM
+
+<aside>
+🚨 **Open Task:** : Add account, address key relationship diagram for clarity
+</aside>
+
+## User stories
+
+1. As an existing account with an ED key but no EVM address alias, I would like to set an ECDSA derived EVM address
+    alias on my account that will identify my account on the EVM.
+2. As an existing account with an EC key but no EVM address alias, I would like to set an ECDSA derived EVM address
+    alias on my account that will identify my account on the EVM.
+3. As an existing account with a complex key but no EVM address alias, I would like to set an ECDSA derived EVM address
+    alias on my account that will identify my account on the EVM.
+5. As an existing account with a newly set ECDSA derived EVM address, I want my account to conform with `ecrecover`
+    expectations as long as I sign the transaction with the ECDSA key that corresponds to the EVM address alias.
+    This key may or may not be the key currently on my account.
+5. As an account with an EVM address alias set after creation, I would like to set an evm address override to my
+    previous long zero address for a `ContractCreate` transaction.
+6. As an account with an EVM address alias set after creation, I would like to set an evm address override to my
+    previous long zero address for a `ContractCall` transaction.
+
+## Specification
+
+The main change to the network is simple - `CryptoUpdate` transactions will support setting a new ECDSA derived
+`evm_address` if the current value is unset.
+
+### Protobuf
+```protobuf
+message CryptoUpdateTransactionBody {
+    ...
+
+    /**
+     * EOA 20-byte address to create that is derived from the keccak-256 hash of a ECDSA_SECP256K1 primitive key.
+     */
+    bytes evm_address = 19;
+}
+```
+
+Additionally, `ContractCreate` and `ContractCall` EVM transactions will need to support the ability to specify the
+a Hedera Num Alias alias EVM address to use on the transaction. This is because on the HAPI side all aliases are
+applicable and thus the flexibility of the API is important to maintain.
+Also, accounts that previously had no ECDSA derived EVM address were likely created via the HAPI flow and it may
+be important for an EOA to utilize the long zero address even after setting a new ECDSA derived EVM address.
+For transactions that utilize the `EthereumTransaction` a compliant ECDSA derived EVM address is provided by default
+when using EVM tools.
+
+```protobuf
+message ContractCreateTransactionBody {
+    ...
+    /**
+    * The 20-byte EVM address to use for the given transaction. This address must be the Hedera num alias of the account.
+    */
+    bytes evm_address_override = 21;
+}
+
+message ContractCallTransactionBody {
+	...
+    /**
+    * The 20-byte EVM address to use for the given transaction. This address must be the Hedera num alias of the account.
+    */
+    bytes evm_address_override = 5;
+}
+```
+
+No change is needed to expose the evm address as it is covered by the `evm_address` property on `TransactionRecord`
+
+### HSCS System Contract API
+The HAS system contract will need to be updated to add support for a `setEVmAddressAlias()` function to expose the
+`CryptoUpdate` HAPI functionality and allow EOAs to call this logic directly from dApps.
+
+### SDK
+
+SDKs will need to update the `AccountUpdateTransaction` to support the `setAlias()` function as it does on
+`AccountCreateTransaction`. This will populate the `evm_address` in the `CryptoUpdateTransactionBody`to be submitted.
+
+`ContractCreateTransaction` and `ContractExecuteTransaction` will need to support a new `setEVmAddressOverride()`
+function to set the `evm_address_override` property on the respective `ContractCreate` and `ContractCall` transactions. 
+
+### Mirror Node
+
+Mirror Nodes should be sure to support the setting of the evm address value on an account when processing a
+`CryptoUpdate` transaction. As in the case of a `CryptoCreate` the new value can be retrieved from the `evm_address`
+property on `TransactionRecord`.
+If no custom logic already exists to ignore this Mirror Nodes will be unimpaired by the change
+
+### Wallets
+
+The HIP provides opportunities for increased user functionality.
+- Wallets are encouraged to create accounts with an ECDSA derived address alias
+- Wallets are encouraged to support the ability for users to set an ECDSA derived alias in the future. This may require
+wallets to support multiple keys for users that may decide to interchange between addresses.
+
+## Backwards Compatibility
+
+This does not break previous functionality but rather adds new scoped support for a change that is possible at account
+creation time. However, it may be said that there is a behaviour change here that is important to note. This change
+is accepted as the benefits of unblocking existing accounts outweighs the cons. The ability to override the address
+also ensure there's a pathway for EOA to set their long zero address if needed.
+Finally, it is appropriate for clients to query mirror node for accurate account details. Clients that do this will
+avoid not be impacted by this change.
+
+## Security Implications
+
+Smart contracts have their logic self contained in byte code. Therefore, the implications of address changes are
+dictated by each smart contract and not the network. A smart contract may cache an EOA address on first interaction and
+utilize that to identify them in future. The cached address could dictate balance access or other privileged access.
+
+As such, an EOA that has interacted with a smart contract using their long zero address and then sets an ECDSA derived
+EVM address after will be responsible for any unexpected interactions with the smart contract.
+It is advised that an EOA in this case first transfer all in contract storage assets to the EVM address prior to
+setting their alias.
+
+## How to Teach This
+
+SDK examples, blogs and tutorials on docs.hedera.com
+
+## Reference Implementation
+
+
+## Rejected Ideas
+
+### Implement HIP 631
+[HIP 631: Account Virtual Addresses](https://hips.hedera.com/hip/hip-631) would have added the ability add evm address
+and specify any one of them as the desired address for use. However, this didn't unblock existing account and offered
+likely complex UX that would overcomplicated the issue at this time. Focusing on setting aliases that were already null
+and supporting evm address only for accounts that migrated themselves provides a solution that is focused and less
+complex.
+
+## Open Issues
+
+While a HIP is in draft, ideas can come up which warrant further discussion. Those ideas should be recorded so people
+know that they are being thought about but do not have a concrete resolution. This helps make sure all issues required
+for the HIP to be ready for consideration are complete and reduces people duplicating prior discussions.
+
+## References
+
+
+
+## Copyright/license
+
+This document is licensed under the Apache License, Version 2.0 -- see [LICENSE](../LICENSE) or
+(https://www.apache.org/licenses/LICENSE-2.0)