about.md

This gist determines keys for the "RADICORE ENCRYPTION CLASS": http://pastebin.com/2j2G83AH.

It relies on knowing the settings, but not the key.

See the demo.php file for a test situation using weak random keys.

It takes approximately 10 seconds to work out a 50 character random key.

One interesting thing is that there are colliding keys for a given plaintext.

For example:

plaintext:

lz~?xr98Mn/zYqFMUj$VY9By !CeTsh[kM3pvLpS]nY+@rnI&fgv4@l_d)EpO1N^|wne kA4

encrypted with

o#1C4zKf{Bg@v4&lUM7t<F+6:QL~eo(FyBIS

is decryptable with

o#1C4zKf{Bg@v4&lUM7t<F+6:LQ~eo(F$BIR

There are lots of examples:

[VFy,/pm+?7Qouv.,gB0fDv0dB6)nUY_]_ tgFc0k>~7vGX)?X84IJD],}k3p:tDkvi ;b,ex:HyA4fcI%3ow{
%`c=*MGU)f^J+YG/4bG+wm`0$aq6KoKz?cER8E(bm!
%`c=*MGU)f@JsYG/4bG+&1`0$=-6KoKz?cER8E(<1!

etc.

So to derive the exact key, you'd need multiple plaintext/ciphertext pairs.

demo.php

<?php

$enc = new encryption_class;

const KEYSPACE = "! #$%&()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^_`abcdefghijklmnopqrstuvwxyz{|}~";
define("KEYSPACE_LEN", strlen(KEYSPACE));

for ($n = 6; $n < 64; $n++) {
    $key = '';
    for ($i = 0; $i < $n; $i++) {
        $key .= substr(KEYSPACE, mt_rand(0, KEYSPACE_LEN - 1), 1);
    }

    $plaintext = "";
    for ($i = 0; $i < 2 * $n; $i++) {
        $plaintext .= substr(KEYSPACE, mt_rand(0, KEYSPACE_LEN-1), 1);
    }

    echo "Trying $n\n";
    $s = microtime(true);
    $k = decodeKey($enc, $enc->encrypt($key, $plaintext, strlen($plaintext)), $plaintext);
    $e = microtime(true);
    if ($k !== $key) {
        echo "Error in  $k\n";
        echo "Should be $key\n";
    }
    echo "Key[$n] in " . number_format($e - $s) . " seconds\n";
}

impl.php

<?php

function decodeKey($enc, $encrypted, $plain) {
    $calls = 0;
    $keylen = [];
    for ($i = 0; $i < 255; $i++) {
        $calls++;
        if ($plain[0] === $enc->decrypt(str_repeat("a", $i), $encrypted, strlen($encrypted))[0]) {
            $keylen[] = $i;
        }
    }
    foreach ($keylen as $len) {
        $try = decodeKeyLen($enc, $encrypted, $plain, "", $len, $calls);
        if ($try) {
            var_dump($calls);
            return $try;
        }
    }
}

function decodeKeyLen($enc, $encrypted, $plain, $prefix, $len, &$calls) {
    $key = $prefix;
    for ($i = strlen($prefix); $i < $len; $i++) {
        $candidates = [];
        for ($j = 0; $j < KEYSPACE_LEN; $j++) {
            $c = substr(KEYSPACE, $j, 1);
            $calls++;
            $tKey = $key . str_repeat($c, $len - $i);
            $t = $enc->decrypt($tKey, $encrypted, strlen($encrypted));
            if (!isset($t[$i + 1]) || $t[$i + 1] === $plain[$i + 1]) {
                $candidates[] = $c;
            }
        }
        if (count($candidates) === 1) {
            $key .= $candidates[0];
        } elseif (empty($candidates)) {
            return false;
        } elseif (count($candidates) === KEYSPACE_LEN) {
            return $key;
        } else {
            foreach ($candidates as $candidate) {
                $try = decodeKeyLen($enc, $encrypted, $plain, $key . $candidate, $len, $calls);
                if ($try) {
                    return $try;
                }
            }
            // if we get here, there was a problem
            return false;
        }
    }
    return $key;
}