EIP: 55
Title: Mixed-case checksum address encoding
Author: Vitalik Buterin
Type: Standard Track
Category: ERC
Status: Accepted
Created: 2016-01-14
Code:
from ethereum import utils
def checksum_encode(addr): # Takes a 20-byte binary address as input
o = ''
v = utils.big_endian_to_int(utils.sha3(addr.hex()))
for i, c in enumerate(addr.hex()):
if c in '0123456789':
o += c
else:
o += c.upper() if (v & (2**(255 - 4*i))) else c.lower()
return '0x'+o
def test(addrstr):
assert(addrstr == checksum_encode(bytes.fromhex(addrstr[2:])))
test('0x5aAeb6053F3E94C9b9A09f33669435E7Ef1BeAed')
test('0xfB6916095ca1df60bB79Ce92cE3Ea74c37c5d359')
test('0xdbF03B407c01E7cD3CBea99509d93f8DDDC8C6FB')
test('0xD1220A0cf47c7B9Be7A2E6BA89F429762e7b9aDb')
In English, convert the address to hex, but if the i
th digit is a letter (ie. it's one of abcdef
) print it in uppercase if the 4*i
th bit of the hash of the lowercase hexadecimal address is 1 otherwise print it in lowercase.
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.
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()
# All caps
0x52908400098527886E0F7030069857D2E4169EE7
0x8617E340B3D01FA5F11F306F4090FD50E238070D
# All Lower
0xde709f2102306220921060314715629080e2fb77
0x27b1fdb04752bbc536007a920d24acb045561c26
# Normal
0x5aAeb6053F3E94C9b9A09f33669435E7Ef1BeAed
0xfB6916095ca1df60bB79Ce92cE3Ea74c37c5d359
0xdbF03B407c01E7cD3CBea99509d93f8DDDC8C6FB
0xD1220A0cf47c7B9Be7A2E6BA89F429762e7b9aDb
Wallet | displays checksummed addresses | rejects invalid mixed-case | rejects too short | rejects too long |
---|---|---|---|---|
Etherwall 2.0.1 | Yes | Yes | Yes | Yes |
Jaxx 1.2.17 | No | Yes | Yes | Yes |
MetaMask 3.7.8 | Yes | Yes | Yes | Yes |
Mist 0.8.10 | Yes | Yes | Yes | Yes |
MyEtherWallet v3.9.4 | Yes | Yes | Yes | Yes |
Parity 1.6.6-beta (UI) | Yes | Yes | Yes | Yes |
Exchange | displays checksummed deposit addresses | rejects invalid mixed-case | rejects too short | rejects too long |
---|---|---|---|---|
Bitfinex | No | Yes | Yes | Yes |
Coinbase | Yes | No | Yes | Yes |
GDAX | Yes | Yes | Yes | Yes |
Kraken | No | No | Yes | Yes |
Poloniex | No | No | Yes | Yes |
Shapeshift | No | No | Yes | Yes |
- EIP 55 issue and discussion ethereum#55
- Python example by @Recmo ethereum#55 (comment)
- Python implementation in
ethereum-utils
- Ethereumjs-util implementation https://github.com/ethereumjs/ethereumjs-util/blob/75f529458bc7dc84f85fd0446d0fac92d991c262/index.js#L452-L466
- Swift implementation in
EthereumKit