🚧 Stagnant Standards Track: Core

EIP-4747: Simplify EIP-161

Simplify EIP-161 and retroactively deprecate unused aspects of it

Authors	Peter Davies (@petertdavies)
Created	2022-02-02
Discussion Link	https://ethereum-magicians.org/t/eip-4747-simplify-eip-161/8246
Requires	EIP-161

Abstract

Simplify the definition of EIP-161, removing the requirement for implementors to support edge cases that are impossible on Ethereum Mainnet.

Motivation

EIP-161 is overly complex and has a number of edge cases that are poorly documented and tested. This EIP takes advantage of the complete removal of all remaining empty accounts in block 14049881 (tx 0xf955834bfa097458a9cf6b719705a443d32e7f43f20b9b0294098c205b4bcc3d) to clarify it, and allows implementors to not implement various edge cases that never occurred and are not possible in the future.

In particular, this EIP permits implementors who do not wish to support historical blocks to not implement state clearing at all.

Specification

The key words “MUST”, “MUST NOT”, “REQUIRED”, “SHALL”, “SHALL NOT”, “SHOULD”, “SHOULD NOT”, “RECOMMENDED”, “MAY”, and “OPTIONAL” in this document are to be interpreted as described in RFC 2119.

Retroactively replace EIP-161, starting from its introduction in block 2675000, with the following rules:

a. When creating an account, set it’s nonce to 1 prior to executing initcode.

b. When performing EVM execution treat all empty accounts as if they do not exist. Any operation that would create an empty account instead leaves it non-existent.

c. If one of the following events happens to an empty account X, it is deleted:

1. X receives a zero value CALL.
2. X is the recipient of a zero value transaction.
3. X is the beneficiary of a SELFDESTRUCT with zero value.

If the transaction, CALL or SELFDESTRUCT is reverted, then the state clearing is also reverted. As a special case on Ethereum Mainnet, in block 2675119 (tx 0xcf416c536ec1a19ed1fb89e4ec7ffb3cf73aa413b3aa9b77d60e4fd81a4296ba), an empty call is made to an empty account at RIPEMD160 (precompile 0x3), the call fails out of gas, but the empty account is removed anyway.

The deletion MAY happen immediately or be processed at the end of the transaction. A client may assume that STATICCALLs to empty accounts never occur and that CALLs to empty accounts in STATICCALL contexts never occur.

On Ethereum Mainnet, the only state clearing events after the start of Byzantium are the two listed below. Clients MAY implement post Byzantium state clearing by hardcoding those events.

• In block 4457731 (tx 0x63791f962e13e6b01ec13d38a8ab66c87c2f5a1768276f866300d900cca808fe), 0xd29DFe5aE95B5C067a91F472Dac0d9be6700A4A9 receives a zero value SELFDESTRUCT and is cleared.

• In block 14049881 (tx 0xf955834bfa097458a9cf6b719705a443d32e7f43f20b9b0294098c205b4bcc3d), the following accounts receive zero value calls and are cleared.

  Accounts cleared

  ``` 0x01a3dd7d158e3b4c9d8d2af0ddcf3df0f5e14463 0x0366c731dd7c095dc08896806765a649c6c0885a 0x056c68da52395f1d42c5ba15c4fb956146a4f2c1 0x070ba92497cd4b88a8a9a60795ca7d7f7de0faa3 0x07a1648ce2bed6721a5d25de3c228a296d03fd52 0x07b14ba68f474529cc0bd6a9bffee2bc4090d185 0x07ea32232e37d44134a3071319d228bdab249a60 0x096b7382500fa11c22c54c0422c5e38899a2e933 0x09f3200441bd60522bcf28f3666f8e8dbd19fb62 0x0ad0f3c60696adece09367a9a11c968fb88560bb 0x0af6181e1db22071f38fc162e1610e29d288de04 0x0cdc7fef8f8d0ee77360060930aada1263b26ff7 0x0dac3d571eb5b884a2550db2791d5ac1efca306b 0x0ec857faba49392080b68dd5074d85f34724d04a 0x0f5054f9c674b37d15915ca8925f231edb3afa8c 0x0f78d535e1faad9a982dca2a76d16da4649f7021 0x104c5b235166f26df54f52666d5e77d9e03e353e 0x106b47175965b6d607008544267c91490672a54f 0x1223d5c03b4d52ebed43f781251098c9138c3dd7 0x1251d13cde439378349f039379e83c2641b6269f 0x12c814cebee6bb08a5d1b9d009332bf8b536d645 0x150c63df3da35e590a6d2f7accf2e6f241ea5f1a 0x15ddf20e4eb8b53b823bc45c9bad2670aad907dd 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0x94cfdec548de92301735dc0b82d8e1f79404ff94 0x96527f3311f44340887c926acc16f0997eb3b955 0x974117faf194885c01513e8d87b38a2291083ed5 0x993424827a5fb2fa97818814ea4027e28150f187 0x9a6f30a5cb46840076edd780da2dbb4bc7c39f24 0x9a74a096b0bb82adfd28494107f2c07f4545723e 0x9af82ec46185641c0ea44679aac8a7e7570be202 0x9e2287a60ed85f6bd80c62c1b7b4130ea1b521dd 0x9fee5b81ee0cbf34c18c52061f1b257d4ccb2702 0xa017226377e775af8e56450301cc035ae72267f8 0xa1b423e024daf925f25296ea2efcf009cc328873 0xa23c0cbfe59e8650277ffa635c59f287cece9087 0xa340b7625eec76b372f2c317fe08a7733f05d09c 0xa4cb6be13c2eace6c0f1157553e3c446f7b38b10 0xa54326267784fae3ffd6800af38099753bb7f470 0xa580086125d040fddd3af9d563285bd0ec4d13e3 0xa88fc7a34ca36b952aa45d94c1e13155042b5e7d 0xac8f4ce2e4eff39c738bf1941350b3b57e8eec4f 0xacb17dca110db022b1aceb5399acba1e9bf577e3 0xae0b03c8d8bf9cf71eda758e9e8b59c70a3b4580 0xae365ff4b0c64413baf6f7dfdb5cd3fb65ad1376 0xaf7e60d02b425b54730b7281a97d1640233704b0 0xaf9846f8098656e7c2f0e53e9ff7d38ec7b7f679 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0xd32bb8bceafc89ff59ba43ce8b6cd65bb06dd7b0 0xd49e9fa792db9d9398c57eabf94ba1b2c709ace7 0xd6b862cf0d009bde0f020ab9d8f96e475069c5c6 0xd747c05d9c8057db608ef7aedabf07e4db0bbe97 0xdb9b40d1b691ced3680e539261b6bc195388b3c0 0xdbcc502093cadd0feb709708c633e2427aeb9c2d 0xdc53001181ddc6a279deea6419443ea0ac0aec9c 0xde3b38cb1050e7b5db39b4cbb2b2b63a1e32cbf6 0xdf1b687a99216ad4ebf9176983bf165be7b25bbe 0xe000662c02a02d8b40aabfcd661594312992311d 0xe30c59e4dc19d7c9ed6eb10d734d4d7ef28403ac 0xe415114089b4b4933e542a5c79af4b6e6cd7abc9 0xe47f0a0e93241d390fe9b99de852682522e847bc 0xe54abbd51e324bf8cf349b6b31c01b043d1ee0e4 0xe57838f777b11fdc428d9e7e67f1187d6251ba1f 0xe5e4b26325d0fbf551367f2cf3b5d01caed6abcf 0xe6655208bd812d833238b560e847014b0aab3b51 0xe6e16a1023af4a8fe54669f3fce7c406801bb333 0xe727bba699fbe82a731dad9476b5234d0038cfa1 0xec361d34a55e24e2f77de7121ae2b7bf11ed0d65 0xed3bf94976eb11d55b955d1369a478620872b57c 0xee93ad447fe6a0e2bbac4952e651b21c0175acad 0xefc5d9cabc0bda8124e1b821e8c86c7e7bf1e4bc 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Rationale

EIP-161 provides that empty accounts (accounts that have zero nonce, zero balance and no code, but that might have storage) can no longer be created and provides mechanism to remove old empty accounts. The last empty accounts were removed in block 14049881 (tx 0xf955834bfa097458a9cf6b719705a443d32e7f43f20b9b0294098c205b4bcc3d).

The complete removal of all empty accounts ensures that certain edgecases of EIP-161 can never occur on Ethereum Mainnet. Continuing to define and test those cases as part of the Ethereum Specification burdens future client implementors with unnecessary technical debt. This EIP declares those cases undefined and leaves clients free to assume they will not occur.

Backwards Compatibility

This EIP is identical to EIP-161 except for the following differences, none of which affect Ethereum Mainnet. The differences are:

“Potentially state-changing operations”

EIP-161 specifies 11 “potentially state-changing operations” that trigger state clearing. All but the 3 listed in this EIP are irrelevant, for the following reasons:

Impossible

• Receiving zero value mining reward/fees (this would become possible after the merge).

Cannot happen to an empty account

• Being the source of a CREATE.
• Being the source of a CALL.
• Being refunded by a SELFDESTRUCT

Causes the account to become non-empty

• Being the sender of a message call transaction.
• Being the sender of a contract creation transaction.
• Being created by a CREATE.
• Being created by a contract creation transaction.

Interaction with STATICCALL

The interaction between STATICCALL and account clearing has never been specified in an EIP. The Ethereum currently testsuite requires that STATICCALL triggers state clearing.

This EIP formally undefines all interactions between STATICCALL and state clearing as it has never happened on Ethereum Mainnet and cannot happen in future.

“At the end of the transaction”

This only makes a difference if an account is deleted and later recreated in the same transaction. This never happens on Ethereum Mainnet.

Test Cases

All test cases involving empty accounts in the Ethereum execution layer test suite shall be removed unless they relate to the Spurious Dragon Hardfork. If a Spurious Dragon test relates involved deprecated edgecase the test must be removed or reworked.

Other networks

Ropsten had empty accounts seeded at genesis. They appear to have been cleared early in Ropsten’s history before the Byzantium hardfork. Ropsten has never been checked for edgecases occurring. All other Ethereum testnets have had EIP-161 from genesis.

As a security precaution all empty accounts on Ethereum Classic have been cleared, but no checks for edgecases occurring have been done. Due to EIP-161’s age the vast majority of EVM compatible networks have supported it from genesis.

Security considerations

This EIP is only equivalent to EIP-161 on Ethereum Mainnet if the following facts are true:

1. No empty accounts are ever touched and then reinstated in the same transaction.
2. The transactions in the Appendix are the only state clearing transactions on Ethereum Mainnet after block 4370000 (start of Byzantium).
3. All empty accounts have been removed on Ethereum Mainnet.

Copyright

Copyright and related rights waived via CC0.

Citation

Please cite this document as:

Peter Davies (@petertdavies), "EIP-4747: Simplify EIP-161 [DRAFT]," Ethereum Improvement Proposals, no. 4747, February 2022. [Online serial]. Available: https://eips.ethereum.org/EIPS/eip-4747.