Merge pull request #654 from cdetrio/eip-55

create file for EIP-55 (mixed-case address checksums)
2025-02-04 19:13:48 +00:00 · 2017-06-26 00:59:55 -06:00 · 2017-06-26 00:59:55 -06:00 · 1b16a7d089
commit 1b16a7d089
parent da05d7eb34 0bf49ff712
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+```
+EIP: 55
+Title: Mixed-case checksum address encoding
+Author: Vitalik Buterin
+Type: Standard Track
+Category: ERC
+Status: Accepted
+Created: 2016-01-14
+```
+
+# Specification
+
+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.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_encode2(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 address is 1 otherwise print it in lowercase.
+
+# Implementation
+
+In javascript:
+
+```js
+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()
+```
+
+# 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.
+
+# Adoption
+
+| Wallet                   | displays checksummed addresses | rejects invalid mixed-case | rejects too short | rejects too long |
+|--------------------------|--------------------------------|----------------------------|-------------------|------------------|
+| 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 support for mixed-case address checksums, as of 2017-05-27:
+
+| 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              |
+
+# References
+
+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
+3. Ethereumjs-util implementation https://github.com/ethereumjs/ethereumjs-util/blob/75f529458bc7dc84f85fd0446d0fac92d991c262/index.js#L452-L466