diff --git a/EIPS/eip-55.md b/EIPS/eip-55.md index 01e18f33..fef1723e 100644 --- a/EIPS/eip-55.md +++ b/EIPS/eip-55.md @@ -4,7 +4,7 @@ Title: Mixed-case checksum address encoding Author: Vitalik Buterin Type: Standard Track Category: ERC -Status: Draft +Status: Accepted Created: 2016-01-14 ``` @@ -13,27 +13,36 @@ Created: 2016-01-14 Code: ``` python +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)) - for i, c in enumerate(addr.encode('hex')): + 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 - i))) else c.lower() + o += c.upper() if (v & (2**(255 - 4*i))) else c.lower() return '0x'+o + +def test(addrstr): + assert(addrstr == checksum_encode2(bytes.fromhex(addrstr[2:]))) + +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 ith bit of the hash of the address (in binary form) is 1 otherwise print it in lowercase. +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 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 -- ~~The average address will have 60 check bits, and less than 1 in 1 million addresses will have less than 32 check bits; this is stronger performance than nearly all other check schemes. Note that the very tiny chance that a given address will have very few check bits is dwarfed by the chance in any scheme that a bad address will randomly pass a check~~ +- 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. -UPDATE: I was actually wrong in my math above. I forgot that the check bits are per-hex-character, not per-bit (facepalm). 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. +# References -Examples: -- `0xCd2a3d9f938e13Cd947eC05ABC7fe734df8DD826` (the "cow" address) -- `0x9Ca0e998dF92c5351cEcbBb6Dba82Ac2266f7e0C` -- `0xcB16D0E54450Cdd2368476E762B09D147972b637` +1. EIP 55 issue and discussion https://github.com/ethereum/eips/issues/55 +2. Python example by @Recmo https://github.com/ethereum/eips/issues/55#issuecomment-261521584