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ERC-55

Mixed-case checksum address encoding

FinalStandards Track: ERC
创建时间: 2016-01-14
Vitalik Buterin <vitalik.buterin@ethereum.org>, Alex Van de Sande <avsa@ethereum.org>
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Specification

Code:

import eth_utils def checksum_encode(addr): # Takes a 20-byte binary address as input hex_addr = addr.hex() checksummed_buffer = "" # Treat the hex address as ascii/utf-8 for keccak256 hashing hashed_address = eth_utils.keccak(text=hex_addr).hex() # Iterate over each character in the hex address for nibble_index, character in enumerate(hex_addr): if character in "0123456789": # We can't upper-case the decimal digits checksummed_buffer += character elif character in "abcdef": # Check if the corresponding hex digit (nibble) in the hash is 8 or higher hashed_address_nibble = int(hashed_address[nibble_index], 16) if hashed_address_nibble > 7: checksummed_buffer += character.upper() else: checksummed_buffer += character else: raise eth_utils.ValidationError( f"Unrecognized hex character {character!r} at position {nibble_index}" ) return "0x" + checksummed_buffer def test(addr_str): addr_bytes = eth_utils.to_bytes(hexstr=addr_str) checksum_encoded = checksum_encode(addr_bytes) assert checksum_encoded == addr_str, f"{checksum_encoded} != expected {addr_str}" test("0x5aAeb6053F3E94C9b9A09f33669435E7Ef1BeAed") test("0xfB6916095ca1df60bB79Ce92cE3Ea74c37c5d359") test("0xdbF03B407c01E7cD3CBea99509d93f8DDDC8C6FB") test("0xD1220A0cf47c7B9Be7A2E6BA89F429762e7b9aDb")

In English, convert the address to hex, but if the ith digit is a letter (ie. it's one of abcdef) print it in uppercase if the 4*ith bit of the hash of the lowercase hexadecimal address is 1 otherwise print it in lowercase.

Rationale

Benefits:

  • Backwards compatible with many hex parsers that accept mixed case, allowing it to be easily introduced over time
  • Keeps the length at 40 characters
  • On average there will be 15 check bits per address, and the net probability that a randomly generated address if mistyped will accidentally pass a check is 0.0247%. This is a ~50x improvement over ICAP, but not as good as a 4-byte check code.

Implementation

In javascript:

const createKeccakHash = require('keccak') function toChecksumAddress (address) { address = address.toLowerCase().replace('0x', '') var hash = createKeccakHash('keccak256').update(address).digest('hex') var ret = '0x' for (var i = 0; i < address.length; i++) { if (parseInt(hash[i], 16) >= 8) { ret += address[i].toUpperCase() } else { ret += address[i] } } return ret }
> toChecksumAddress('0xfb6916095ca1df60bb79ce92ce3ea74c37c5d359')
'0xfB6916095ca1df60bB79Ce92cE3Ea74c37c5d359'

Note that the input to the Keccak256 hash is the lowercase hexadecimal string (i.e. the hex address encoded as ASCII):

    var hash = createKeccakHash('keccak256').update(Buffer.from(address.toLowerCase(), 'ascii')).digest()

Test Cases

# All caps
0x52908400098527886E0F7030069857D2E4169EE7
0x8617E340B3D01FA5F11F306F4090FD50E238070D
# All Lower
0xde709f2102306220921060314715629080e2fb77
0x27b1fdb04752bbc536007a920d24acb045561c26
# Normal
0x5aAeb6053F3E94C9b9A09f33669435E7Ef1BeAed
0xfB6916095ca1df60bB79Ce92cE3Ea74c37c5d359
0xdbF03B407c01E7cD3CBea99509d93f8DDDC8C6FB
0xD1220A0cf47c7B9Be7A2E6BA89F429762e7b9aDb
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