KIP 97: Signed Data Standard

Simple Summary

This is to standardize message signing methods different from those of Ethereum.

Abstract

This standard proposes a specification about how to handle signed data in Klaytn.

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 in Klaytn and Ethereum solved this by EIP-191 standard. Additionally, the signatures are different when using Metamask and Kaikas because they have the different preamble.

Specification

This document is heavily derived from EIP-191 written by Martin Holst Swende and Nick Johnson.

We propose the following format for signed_data:

0x19 <1 byte version> <version specific data> <data to sign>

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 signed_data can never be an Klaytn transaction.

The following format is prepended before hashing in personal_sign:

"\x19Klaytn Signed Message:\n" + len(message)

Using 0x19 thus makes it possible to extend the scheme by defining a version 0x4b (K) to handle these kinds of signatures.

Registry of version bytes

Version 0x4b (K)

0x19 <0x4b (K)> <laytn Signed Message:\n" + len(message)> <data to sign>

The version 0x4b (K) has <laytn Signed Message:\n" + len(message)> for the version-specific data. The data to sign can be any arbitrary data.

NB: The K in Klaytn Signed Message refers to the version byte 0x4b. The character K is 0x4b in hexadecimal which makes the remainder, laytn Signed Message:\n + len(message), the version-specific data.

Specification of the caver.js API

caver.klay.accounts.sign('Some data', '0x{private key}');

Returns

{
    message: 'Some data',
    messageHash: '0x8ed2036502ed7f485b81feaec1c581d236a8b711e55a24077724879c8a263c2a',
    v: '0x1b',
    r: '0x4a57bcff1637346a4323a67acd7a478514d9f00576f42942d50a5ca0e4b0342b',
    s: '0x5914e19a8ebc10ce1450b00a3b9c1bf0ce01909bca3ffdead1aa3a791a97b5ac',
    signature: '0x4a57bcff1637346a4323a67acd7a478514d9f00576f42942d50a5ca0e4b0342b5914e19a8ebc10ce1450b00a3b9c1bf0ce01909bca3ffdead1aa3a791a97b5ac1b'
}

Backwards Compatibility

• caver-js already sign in this format.
• caver-java already sign in this format.

Reference

EIP-191

Copyright

Copyright and related rights waived via CC0.