require_once '../01-basics/06-break-repeating-key-xor.php';
require_once '18-implement-ctr-the-stream-cipher-mode.php';
$plaintexts = array_map('base64_decode', file('20-data.txt', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES));
$key = getRandomBytes(16);
$ciphertexts = array_map('encryptAES128CTR', $plaintexts, array_fill(0, count($plaintexts), $key));
$cipherLens = array_map('strlen', $ciphertexts);
// challenge text says use a common length, but we can recover more if we don't
// this is because after transposition there's still enough data to statistically recover more
/*
$minLength = min($cipherLens);
$truncated = array_map('str_split', $ciphertexts, array_fill(0, count($plaintexts), $minLength));
$truncated = array_column($truncated, 0);
*/
$truncated = $ciphertexts;
// some copy/paste/tweak from challenge 6
print "\nSolving keys based on English Language scoring:\n";
$blocks = transposeBlocks($ciphertexts);
$englishLanguageWeights['/'] = 0;
list($topScores, $topChars) = scoreSingleByteXORStrings($blocks, $englishLanguageWeights, 20);
$potentialKey = implode(array_map('chr', $topChars));
foreach ($truncated as $k => $ciphertext) {
$recovered = $ciphertext ^ $potentialKey;
print "{$k}: {$recovered}\n";
}
print "\n\nSome texts will not be fully recovered.\nThis is expected for simple automatic statistical recovery.\n\n\n";
foreach ($truncated as $k => $ciphertext) {
$recovered = $ciphertext ^ $potentialKey;
if ($recovered !== $plaintexts[$k]) {
print "Cracked : {$recovered}\nOriginal: {$plaintexts[$k]}\n\n";
}
}
function scoreSingleByteXORStrings(array $strings, array $weights, $penalty = 0)
{
$topScores = [];
$topChars = [];
foreach ($strings as $pos => $string) {
$scores = scoreSingleByteXOR($string, $weights, $penalty);
arsort($scores);
$topScores[$pos] = current($scores);
$topChars[$pos] = key($scores);
}
return [$topScores, $topChars];
}
// don't output if we're included into another script.
if (!debug_backtrace()) {
$encrypted = array_map('hex2bin', file('04-data.txt', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES));
list($topScores, $topChars) = scoreSingleByteXORStrings($encrypted, $englishLanguageWeights);
arsort($topScores);
print "Highest scoring strings indexes and characters:\n";
$i = 0;
foreach ($topScores as $k => $v) {
$c = $topChars[$k];
print "{$k} - {$c} - {$v}\n";
if (++$i === 3) {
break;
}
}
print "\nDecrypted strings:\n";
$i = 0;
foreach ($topScores as $k => $v) {
$encryptedLen = strlen($encrypted[$k]);
$decypted = $encrypted[$k] ^ str_repeat(chr($topChars[$k]), $encryptedLen);
