CODEWITHSUNDEEP
cradix
farmdve
farmdve

Reputation: 786

How do I base58 encode a string?

char (* text)[1][45+1];
text = calloc(5000,(130+1));
strcpy(0[*text],"sometext)");

Now I want to encode "sometext" to base58, however, I do not know how, and oddly enough, there isn't one example of BASE58 in C.

The base58 encoding I'm interested in uses these symbols:

123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ

It's been optimized to lessen the risk of mis-reading, so 0 and 'O' are both gone, for instance.

P.S Don't mind the weird allocation and declaration of the variables, I was experimenting.

Upvotes: 11

Views: 24732

Answers (5)

Вадим А
Вадим А

Reputation: 31

My simple code with Crypto++ library: 


  string base58_encode(Integer num, string vers)
  {
    string alphabet[58] = {"1","2","3","4","5","6","7","8","9","A","B","C","D","E","F",
    "G","H","J","K","L","M","N","P","Q","R","S","T","U","V","W","X","Y","Z","a","b","c",
    "d","e","f","g","h","i","j","k","m","n","o","p","q","r","s","t","u","v","w","x","y","z"};
    int base_count = 58; string encoded; Integer div; Integer mod;
    while (num >= base_count)
    {
        div = num / base_count;   mod = (num - (base_count * div));
        encoded = alphabet[ mod.ConvertToLong() ] + encoded;   num = div;
    }
    encoded = vers + alphabet[ num.ConvertToLong() ] + encoded;
    return encoded;
  }
It's just for cryptocurrency wallets. string can be changed for other tasks.

Upvotes: 2

Adam Mackler
Adam Mackler

Reputation: 2080

Here is an implementation that seems to be pure c.

https://github.com/trezor/trezor-crypto/blob/master/base58.c

Upvotes: 1

Amithings
Amithings

Reputation: 91

Here's an implementation in PHP for large numbers I've created for Amithings, beyond the integers (Integer -> http://php.net/manual/en/language.types.integer.php).

For example, try the example below (Don't forget to pass your ID to the function in string format. Use the PHP function strval()):

$number = '123456789009876543211234567890';
$result = base58_encode($number);
echo('Encoded: ' . $result . '<br>');
echo('Decoded: ' . base58_decode($result) . '<br>');

Important: You may consider to change this routine by including some sort of key/password/encryption to ensure that others can not decode your database IDs.

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);
}

function base58_decode($input)
{
    $alphabet = '123456789abcdefghijkmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ';
    $base_count = strval(strlen($alphabet));
    $decoded = strval(0);
    $multi = strval(1);
    while (strlen($input) > 0)
    {
        $digit = substr($input, strlen($input) - 1);
        $decoded = bcadd($decoded, bcmul($multi, strval(strpos($alphabet, $digit))));
        $multi = bcmul($multi, $base_count);
        $input = substr($input, 0, strlen($input) - 1);
    }
    return($decoded);
}

Upvotes: 9

user2387532
user2387532

Reputation: 71

Satoshi has the reference implementation (https://github.com/bitcoin/bitcoin/blob/master/src/base58.h)

However, he uses some utility bignum class to do it, and it's in C++. If you have access to a bignum library, you just keep dividing by 58 until the number is broken up. If you don't have a bignum library, AFAIK you're outta luck.

Upvotes: 7

unwind
unwind

Reputation: 399713

You're not supposed to encode strings, you're supposed to encode integers.

If starting with a string, you must first decide how to interpret it as an integer (might be base128, or something), then re-encode in base58.

Upvotes: 8

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