ERC-191: Signed Data Standard Ethereum Improvement Proposals AllCoreNetworkingInterfaceERCMetaInformational Standards Track: ERC ERC-191: Signed Data Standard Authors Martin Holst Swende (@holiman), Nick Johnson  Created 2016-01-20 Table of Contents Abstract Motivation Specification Registry of version bytes Example Copyright Abstract This ERC proposes a specification about how to handle signed data in Ethereum contracts. Motivation Several multisignature wallet implementations have been created which accepts presigned transactions. A presigned transaction is a chunk of binary signed_data, along with signature (r, s and v). The interpretation of the signed_data has not been specified, leading to several problems: Standard Ethereum transactions can be submitted as signed_data. An Ethereum transaction can be unpacked, into the following components: RLP (hereby called RLPdata), r, s and v. If there are no syntactical constraints on signed_data, this means that RLPdata can be used as a syntactically valid presigned transaction. Multisignature wallets have also had the problem that a presigned transaction has not been tied to a particular validator, i.e a specific wallet. Example: Users A, B and C have the 2/3-wallet X Users A, B and D have the 2/3-wallet Y User A and B submit presigned transactions to X. Attacker can now reuse their presigned transactions to X, and submit to Y. Specification We propose the following format for signed_data 0x19 <1 byte version> . The initial 0x19 byte is intended to ensure that the signed_data is not valid RLP. For a single byte whose value is in the [0x00, 0x7f] range, that byte is its own RLP encoding. That means that any signed_data cannot be one RLP-structure, but a 1-byte RLP payload followed by something else. Thus, any EIP-191 signed_data can never be an Ethereum transaction. Additionally, 0x19 has been chosen because since ethereum/go-ethereum#2940 , the following is prepended before hashing in personal_sign: "\x19Ethereum Signed Message:\n" + len(message). Using 0x19 thus makes it possible to extend the scheme by defining a version 0x45 (E) to handle these kinds of signatures. Registry of version bytes Version byte EIP Description 0x00 191 Data with intended validator 0x01 712 Structured data 0x45 191 personal_sign messages Version 0x00 0x19 <0x00> The version 0x00 has for the version specific data. In the case of a Multisig wallet that perform an execution based on a passed signature, the validator address is the address of the Multisig itself. The data to sign could be any arbitrary data. Version 0x01 The version 0x01 is for structured data as defined in EIP-712 Version 0x45 (E) 0x19 <0x45 (E)> The version 0x45 (E) has for the version-specific data. The data to sign can be any arbitrary data. NB: The E in Ethereum Signed Message refers to the version byte 0x45. The character E is 0x45 in hexadecimal which makes the remainder, thereum Signed Message:\n + len(message), the version-specific data. Example The following snippets has been written in Solidity 0.8.0. Version 0x00 function signatureBasedExecution(address target, uint256 nonce, bytes memory payload, uint8 v, bytes32 r, bytes32 s) public payable { // Arguments when calculating hash to validate // 1: byte(0x19) - the initial 0x19 byte // 2: byte(0) - the version byte // 3: address(this) - the validator address // 4-6 : Application specific data bytes32 hash = keccak256(abi.encodePacked(byte(0x19), byte(0), address(this), msg.value, nonce, payload)); // recovering the signer from the hash and the signature addressRecovered = ecrecover(hash, v, r, s); // logic of the wallet // if (addressRecovered == owner) executeOnTarget(target, payload); } Copyright Copyright and related rights waived via CC0. Citation Please cite this document as: Martin Holst Swende (@holiman), Nick Johnson , "ERC-191: Signed Data Standard," Ethereum Improvement Proposals, no. 191, January 2016. [Online serial]. Available: https://eips.ethereum.org/EIPS/eip-191. Ethereum Improvement Proposals Ethereum Improvement Proposals ethereum/EIPs Ethereum Improvement Proposals (EIPs) describe standards for the Ethereum platform, including core protocol specifications, client APIs, and contract standards.