CODEWITHSUNDEEP
phphashpublic-key-encryptionbitcoin
anthonyc
anthonyc

Reputation: 187

Hashing from a public key to a bitcoin address in php

I am trying to follow the instructions required to turn a 65 byte public key into a bitcoin address using php. The instructions are quite explicit. Can anyone help me with the practicality of doing that in php?

Instructions are

1 - Take the corresponding public key generated with it (65 bytes, 1 byte 0x04, 32 bytes corresponding to X coordinate, 32 bytes corresponding to Y coordinate)

0450863AD64A87AE8A2FE83C1AF1A8403CB53F53E486D8511DAD8A04887E5B23522CD470243453A299FA9E77237716103ABC11A1DF38855ED6F2EE187E9C582BA6

2 - Perform SHA-256 hashing on the public key

600FFE422B4E00731A59557A5CCA46CC183944191006324A447BDB2D98D4B408

3 - Perform RIPEMD-160 hashing on the result of SHA-256

010966776006953D5567439E5E39F86A0D273BEE

4 - Add version byte in front of RIPEMD-160 hash (0x00 for Main Network)

00010966776006953D5567439E5E39F86A0D273BEE

5 - Perform SHA-256 hash on the extended RIPEMD-160 result

445C7A8007A93D8733188288BB320A8FE2DEBD2AE1B47F0F50BC10BAE845C094

6 - Perform SHA-256 hash on the result of the previous SHA-256 hash

D61967F63C7DD183914A4AE452C9F6AD5D462CE3D277798075B107615C1A8A30

7 - Take the first 4 bytes of the second SHA-256 hash. This is the address checksum

D61967F6

8 - Add the 4 checksum bytes from point 7 at the end of extended RIPEMD-160 hash from point 4. This is the 25-byte binary Bitcoin Address.

00010966776006953D5567439E5E39F86A0D273BEED61967F6

9 - Convert the result from a byte string into a base58 string using Base58Check encoding. This is the most commonly used Bitcoin Address format

16UwLL9Risc3QfPqBUvKofHmBQ7wMtjvM

My first attempt is 

// step 1

$publickey='0450863AD64A87AE8A2FE83C1AF1A8403CB53F53E486D8511DAD8A04887E5B23522CD470243453A299FA9E77237716103ABC11A1DF38855ED6F2EE187E9C582BA6';
$step1=$publickey;

echo "step1 ".$publickey."<br>";

// step 2

$step2=hash("sha256",$step1);
echo "step2 ".$step2."<br>";

// step 3

$step3=hash('ripemd160',$step2);
echo "step3 ".$step3."<br>";

// step 4

$step4="00".$step3;
echo "step4 ".$step4."<br>";

// step 5

$step5=hash("sha256",$step4);
echo "step5 ".$step5."<br>";

// step 6

$step6=hash("sha256",$step5);
echo "step6 ".$step6."<br>";

// step 7

$checksum=substr($step6,0,8);
echo "step7 ".$checksum."<br>";

// step 8

$step8=$step4.$checksum;
echo "step8 ".$step8."<br>";

//step 9

$step9=base58_encode($step8);
echo "step9 ".$step9."<br><br>";

This fails at the first step. Any help appreciated.

This is the output

step1 0450863AD64A87AE8A2FE83C1AF1A8403CB53F53E486D8511DAD8A04887E5B23522CD470243453A299FA9E77237716103ABC11A1DF38855ED6F2EE187E9C582BA6
step2 32511e82d56dcea68eb774094e25bab0f8bdd9bc1eca1ceeda38c7a43aceddce
step3 7528c664cdc34c5ce809778eb688d32f89a538c0
step4 007528c664cdc34c5ce809778eb688d32f89a538c0
step5 86e76f4ff0bf0387339ac70a552e0fed615f7def34cc4809df1429e243f6c1fa
step6 b885b7225b370e7ff27ee0afb4f89b52b8675d5dc342d63de3abe7535f86cadb
step7 b885b722
step8 007528c664cdc34c5ce809778eb688d32f89a538c0b885b722
step9 1

Base58 function is

function base58_encode($input)
{
    $alphabet =     '123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ';
    $base_count = strval(strlen($alphabet));
    $encoded = '';
    while (floatval($input) >= floatval($base_count))
    {
        $div = bcdiv($input, $base_count);
        $mod = bcmod($input, $base_count);
        $encoded = substr($alphabet, intval($mod), 1) . $encoded;
        $input = $div;
    }
    if (floatval($input) > 0)
    {
        $encoded = substr($alphabet, intval($input), 1) . $encoded;
    }
    return($encoded);
}

Upvotes: 2

Views: 9106

Answers (4)

Nemo Kozeba
Nemo Kozeba

Reputation: 21

Very Important!

Replace this: '123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ'

With this: '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'

Using the wrong code here would cause Bitcoin transactions to fail or worse, cause coins to disappear to a phantom wallet where they can never be retrieved.

I am not a developer but I confirmed the correction. The Base58 symbol chart is here, https://en.bitcoin.it/wiki/Base58Check_encoding

I checked my work here http://brainwallet.org/

Enter the passphrase: "test address" without the quotes.

The public key is then: 047969a753f71135d4c792f384e546cd508514024b4ee40d12a014019b77d1b292763dfb8a108cf7a7119f80ca4a06e81b92464f5d8a7544d52cd2e641023a96d7

Your address result : 1gBG1mbVtyNTgGZhggJ21A6mnjbNtqPCSr

My result: 1Gch1MBvUZotGhzHGGj21b6MNKBoURpdsS

brainwallet.org result: 1Gch1MBvUZotGhzHGGj21b6MNKBoURpdsS

I hope this saves someone from a time consuming or costly error.

Upvotes: 2

anthonyc
anthonyc

Reputation: 187

Solution below with thanks to Sammitch for spotting syntax and providing the base conversions.

<?php

// step 1

$publickey='0450863AD64A87AE8A2FE83C1AF1A8403CB53F53E486D8511DAD8A04887E5B23522CD470243453A299FA9E77237716103ABC11A1DF38855ED6F2EE187E9C582BA6';

$step1=hexStringToByteString($publickey);

echo "step1 ".$publickey."<br>";

// step 2

$step2=hash("sha256",$step1);
echo "step2 ".$step2."<br>";

// step 3

$step3=hash('ripemd160',hexStringToByteString($step2));
echo "step3 ".$step3."<br>";

// step 4

$step4="00".$step3;
echo "step4 ".$step4."<br>";

// step 5

$step5=hash("sha256",hexStringToByteString($step4));
echo "step5 ".$step5."<br>";

// step 6

$step6=hash("sha256",hexStringToByteString($step5));
echo "step6 ".$step6."<br>";

// step 7

$checksum=substr($step6,0,8);
echo "step7 ".$checksum."<br>";

// step 8

$step8=$step4.$checksum;
echo "step8 ".$step8."<br>";

// step 9
// base conversion is from hex to base58 via decimal. 
// Leading hex zero converts to 1 in base58 but it is dropped
// in the intermediate decimal stage.  Simply added back manually.

$step9="1".bc_base58_encode(bc_hexdec($step8));
echo "step9 ".$step9."<br><br>";

?>

hash requires a byte string not a hex string. hexStringToByteString is

function hexStringToByteString($hexString){
    $len=strlen($hexString);

    $byteString="";
    for ($i=0;$i<$len;$i=$i+2){
        $charnum=hexdec(substr($hexString,$i,2));
        $byteString.=chr($charnum);
    }

return $byteString;
}

base conversion (thanks to Sammitch - amended to use Bitcoin base58)

// BCmath version for huge numbers
function bc_arb_encode($num, $basestr) {
    if( ! function_exists('bcadd') ) {
        Throw new Exception('You need the BCmath extension.');
    }

    $base = strlen($basestr);
    $rep = '';

    while( true ){
        if( strlen($num) < 2 ) {
            if( intval($num) <= 0 ) {
                break;
            }
        }
        $rem = bcmod($num, $base);
        $rep = $basestr[intval($rem)] . $rep;
        $num = bcdiv(bcsub($num, $rem), $base);
    }
    return $rep;
}

function bc_arb_decode($num, $basestr) {
    if( ! function_exists('bcadd') ) {
        Throw new Exception('You need the BCmath extension.');
    }

    $base = strlen($basestr);
    $dec = '0';

    $num_arr = str_split((string)$num);
    $cnt = strlen($num);
    for($i=0; $i < $cnt; $i++) {
        $pos = strpos($basestr, $num_arr[$i]);
        if( $pos === false ) {
            Throw new Exception(sprintf('Unknown character %s at offset %d', $num_arr[$i], $i));
        }
        $dec = bcadd(bcmul($dec, $base), $pos);
    }
    return $dec;
}


// base 58 alias
function bc_base58_encode($num) {   
    return bc_arb_encode($num, '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz');
}
function bc_base58_decode($num) {
    return bc_arb_decode($num, '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz');
}

//hexdec with BCmath
function bc_hexdec($num) {
    return bc_arb_decode(strtolower($num), '0123456789abcdef');
}
function bc_dechex($num) {
    return bc_arb_encode($num, '0123456789abcdef');
}

final output 

step1 0450863AD64A87AE8A2FE83C1AF1A8403CB53F53E486D8511DAD8A04887E5B23522CD470243453A299FA9E77237716103ABC11A1DF38855ED6F2EE187E9C582BA6
step2 600ffe422b4e00731a59557a5cca46cc183944191006324a447bdb2d98d4b408
step3 010966776006953d5567439e5e39f86a0d273bee
step4 00010966776006953d5567439e5e39f86a0d273bee
step5 445c7a8007a93d8733188288bb320a8fe2debd2ae1b47f0f50bc10bae845c094
step6 d61967f63c7dd183914a4ae452c9f6ad5d462ce3d277798075b107615c1a8a30
step7 d61967f6
step8 00010966776006953d5567439e5e39f86a0d273beed61967f6
step9 16UwLL9Risc3QfPqBUvKofHmBQ7wMtjvM

Upvotes: 6

Sammitch
Sammitch

Reputation: 32232

Your problems are as follow:

  1. Variable names $publickey and $publicKey are not equivalent.
  2. $checksum=substr($step6,0,4); should be $checksum=substr($step6,0,8); because you need two hex chars to represent one byte.
  3. $step8=$step4+$checksum; should be $step8=$step4.$checksum;

Also, I don't know where your base58_encode() function comes from, but I hope it uses BCmath, because the number represented by 00ba084d3f143f2896809d3f1d7dffed472b39d8de7a39cf51 [step 8's result] is too large for PHP to handle internally.

edit

I'm super bored at work today, here's my conversion code with bonus BCmath for ginormous [say, 58-digit?] numbers.

<?php

// original arbitrary encode function
function arb_encode($num, $basestr) {
    $base = strlen($basestr);
    $rep = '';

    while($num > 0) {
        $rem = $num % $base;
        $rep = $basestr[$rem] . $rep;
        $num = ($num - $rem) / $base;
    }
    return $rep;
}

function arb_decode($num, $basestr) {
    $base = strlen($basestr);
    $dec = 0;

    $num_arr = str_split((string)$num);
    $cnt = strlen($num);
    for($i=0; $i < $cnt; $i++) {
        $pos = strpos($basestr, $num_arr[$i]);
        if( $pos === false ) {
            Throw new Exception(sprintf('Unknown character %s at offset %d', $num_arr[$i], $i));
        }
        $dec = ($dec * $base) + $pos;
    }
    return $dec;
}

// BCmath version for huge numbers
function bc_arb_encode($num, $basestr) {
    if( ! function_exists('bcadd') ) {
        Throw new Exception('You need the BCmath extension.');
    }

    $base = strlen($basestr);
    $rep = '';

    while( true ){
        if( strlen($num) < 2 ) {
            if( intval($num) <= 0 ) { break; }
        }
        $rem = bcmod($num, $base);
        $rep = $basestr[intval($rem)] . $rep;
        $num = bcdiv(bcsub($num, $rem), $base);
    }
    return $rep;
}

function bc_arb_decode($num, $basestr) {
    if( ! function_exists('bcadd') ) {
        Throw new Exception('You need the BCmath extension.');
    }

    $base = strlen($basestr);
    $dec = '0';

    $num_arr = str_split((string)$num);
    $cnt = strlen($num);
    for($i=0; $i < $cnt; $i++) {
        $pos = strpos($basestr, $num_arr[$i]);
        if( $pos === false ) {
            Throw new Exception(sprintf('Unknown character %s at offset %d', $num_arr[$i], $i));
        }
        $dec = bcadd(bcmul($dec, $base), $pos);
    }
    return $dec;
}


// base 58 alias
function bc_base58_encode($num) {
    return bc_arb_encode($num, '123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ');
}
function bc_base58_decode($num) {
    return bc_arb_decode($num, '123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ');
}

//hexdec with BCmath
function bc_hexdec($num) {
    return bc_arb_decode(strtolower($num), '0123456789abcdef');
}
function bc_dechex($num) {
    return bc_arb_encode($num, '0123456789abcdef');
}

// example
$orig    = '00ba084d3f143f2896809d3f1d7dffed472b39d8de7a39cf51';
$bten    = bc_hexdec($orig);
$base58  = bc_base58_encode($bten);
$backten = bc_base58_decode($base58);
$back    = bc_dechex($backten);
echo "Orig: " . $orig . "\n";
echo "bten: " . $bten . "\n";
echo "58:   " . $base58 . "\n";
echo "ag10: " . $backten . "\n";
echo "Back:   " . $back  . "\n";

edit2

Don't use base_convert() for numbers this large, it appears to be unreliable. I was writing the necessary bc_arb_decode() counterparts and found that the input and output were differing using base_convert() versus arb_convert($num, '0123456789abcdef'); and after comparing the results with Wolfram Alpha it seems that PHP is incorrectly converting the number.

Hex:           00ba084d3f143f2896809d3f1d7dffed472b39d8de7a39cf51
PHP's decode:  4561501878697786606686086062428080084446806606846864824262
Mine:          4561501878697784703577561586669353227270827349968709865297
Wolfram Alpha: 4561501878697784703577561586669353227270827349968709865297

You can see that PHP is way off. [1.9E42 aka 1.9 quintillion septillion] I've updated my code to include the arb_decode() functions which appear to do things correctly.

Upvotes: 2

user1864610
user1864610

Reputation:

Look carefully at your variable names. $publickey is not the same as $publicKey - note capitalisation.

Upvotes: 2

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