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I've seen a few Bitcoin Address form validation scripts for various languages, but surprisingly can't really find anything for two common web languages, Javascript and PHP.
Here's one for Python, but is there one for PHP and/or JS?
from hashlib import sha256
digits58 = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
def decode_base58(bc, length):
n = 0
for char in bc:
n = n * 58 + digits58.index(char)
return n.to_bytes(length, 'big')
def check_bc(bc):
bcbytes = decode_base58(bc, 25)
return bcbytes[-4:] == sha256(sha256(bcbytes[:-4]).digest()).digest()[:4]
if __name__ == '__main__':
bc = '1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i'
assert check_bc(bc)
assert not check_bc( bc.replace('N', 'P', 1) )
assert check_bc('1111111111111111111114oLvT2')
assert check_bc("17NdbrSGoUotzeGCcMMCqnFkEvLymoou9j")
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Here's a JSFiddle: http://jsfiddle.net/timrpeterson/XsCQq/2/
And here's the full code upon which the JSFiddle is based:
<html>
<head>
<script type="text/javascript" src="http://dl.dropboxusercontent.com/u/28441300/BigInt.js"></script>
<script type="text/javascript" src="http://dl.dropboxusercontent.com/u/28441300/sha256.js"></script>
</head>
<body>
<div id="text">
</div>
<script type="text/javascript">
var address = "1Eym7pyJcaambv8FG4ZoU8A4xsiL9us2zz";
if (check(address)) {
document.getElementById('text').innerHTML += "valid";
} else {
document.getElementById('text').innerHTML += "invalid";
}
function check(address) {
var decoded = base58_decode(address);
if (decoded.length != 25) return false;
var cksum = decoded.substr(decoded.length - 4);
var rest = decoded.substr(0, decoded.length - 4);
var good_cksum = hex2a(sha256_digest(hex2a(sha256_digest(rest)))).substr(0, 4);
if (cksum != good_cksum) return false;
return true;
}
function base58_decode(string) {
var table = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz';
var table_rev = new Array();
var i;
for (i = 0; i < 58; i++) {
table_rev[table[i]] = int2bigInt(i, 8, 0);
}
var l = string.length;
var long_value = int2bigInt(0, 1, 0);
var num_58 = int2bigInt(58, 8, 0);
var c;
for(i = 0; i < l; i++) {
c = string[l - i - 1];
long_value = add(long_value, mult(table_rev[c], pow(num_58, i)));
}
var hex = bigInt2str(long_value, 16);
var str = hex2a(hex);
var nPad;
for (nPad = 0; string[nPad] == table[0]; nPad++);
var output = str;
if (nPad > 0) output = repeat("\0", nPad) + str;
return output;
}
function hex2a(hex) {
var str = '';
for (var i = 0; i < hex.length; i += 2)
str += String.fromCharCode(parseInt(hex.substr(i, 2), 16));
return str;
}
function a2hex(str) {
var aHex = "0123456789abcdef";
var l = str.length;
var nBuf;
var strBuf;
var strOut = "";
for (var i = 0; i < l; i++) {
nBuf = str.charCodeAt(i);
strBuf = aHex[Math.floor(nBuf/16)];
strBuf += aHex[nBuf % 16];
strOut += strBuf;
}
return strOut;
}
function pow(big, exp) {
if (exp == 0) return int2bigInt(1, 1, 0);
var i;
var newbig = big;
for (i = 1; i < exp; i++) {
newbig = mult(newbig, big);
}
return newbig;
}
function repeat(s, n){
var a = [];
while(a.length < n){
a.push(s);
}
return a.join('');
}
</script>
</body>
</html>
And here is a PHP example (assuming your have PHP BC-Math):
<?php
function checkAddress($address)
{
$origbase58 = $address;
$dec = "0";
for ($i = 0; $i < strlen($address); $i++)
{
$dec = bcadd(bcmul($dec,"58",0),strpos("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz",substr($address,$i,1)),0);
}
$address = "";
while (bccomp($dec,0) == 1)
{
$dv = bcdiv($dec,"16",0);
$rem = (integer)bcmod($dec,"16");
$dec = $dv;
$address = $address.substr("0123456789ABCDEF",$rem,1);
}
$address = strrev($address);
for ($i = 0; $i < strlen($origbase58) && substr($origbase58,$i,1) == "1"; $i++)
{
$address = "00".$address;
}
if (strlen($address)%2 != 0)
{
$address = "0".$address;
}
if (strlen($address) != 50)
{
return false;
}
if (hexdec(substr($address,0,2)) > 0)
{
return false;
}
return substr(strtoupper(hash("sha256",hash("sha256",pack("H*",substr($address,0,strlen($address)-8)),true))),0,8) == substr($address,strlen($address)-8);
}
?>
Here is a better version of @Tim-Peterson 's answer. It fixes the base58 implementation he was using (which would not validate the address "12EJmB3cMGRNveskzA7g7kxW32gSbo2dHF".
I combined the validation code with all the needed libraries and removed a lot that wasn't needed. It only exposes a single api: "checkAddress". I created a little home-page for it, where you can download the module source or the minified version: http://www.julianhaight.com/javascript.shtml
The corrected base58_decode (from https://github.com/cryptocoinjs/bs58):
// from https://github.com/cryptocoinjs/bs58
// Base58 encoding/decoding
// Originally written by Mike Hearn for BitcoinJ
// Copyright (c) 2011 Google Inc
// Ported to JavaScript by Stefan Thomas
// Merged Buffer refactorings from base58-native by Stephen Pair
// Copyright (c) 2013 BitPay Inc
var ALPHABET = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
var ALPHABET_MAP = {}
for(var i = 0; i < ALPHABET.length; i++) {
ALPHABET_MAP[ALPHABET.charAt(i)] = i
}
var BASE = 58
function base58_decode(string) {
if (string.length === 0) return []
var i, j, bytes = [0]
for (i = 0; i < string.length; i++) {
var c = string[i]
if (!(c in ALPHABET_MAP)) throw new Error('Non-base58 character')
for (j = 0; j < bytes.length; j++) bytes[j] *= BASE
bytes[0] += ALPHABET_MAP[c]
var carry = 0
for (j = 0; j < bytes.length; ++j) {
bytes[j] += carry
carry = bytes[j] >> 8
bytes[j] &= 0xff
}
while (carry) {
bytes.push(carry & 0xff)
carry >>= 8
}
}
// deal with leading zeros
for (i = 0; string[i] === '1' && i < string.length - 1; i++) bytes.push(0)
bytes = bytes.reverse()
output = '';
for (i=0; i<bytes.length; i++) {
output += String.fromCharCode(bytes[i]);
}
return output;
}
Bitcoin Address (example: 3QJmV3qfvL9SuYo34YihAf3sRCW3qSinyC) is not valid in many the PHP examples. One of the example which works fine especially to the above address is:
Click here to see the PHP Function to validate Bitcoin Address
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