base64 in PHP Otp Library - php

Question

I trying to make some simple library for encrypting files in PHP with OTP method. My problem is that some chars in decrypted code are different than original. I worked on it almost one week but without result. Is there problem with base64 chars or with encoding/decoding mechanism ?
Many thanks for the answers.
final class Otp
{
private static $charSet = array('+','/','0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K','L',
'M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r',
's','t','u','v','w','x','y','z');
public static function encryptFile($originalFilePath, $encryptedFilePath, $keyFilePath)
{
if(!self::existsFile($keyFilePath) || !self::existsFile($encryptedFilePath)) {
if($originalFileData = self::existsFile($originalFilePath)) {
$originalFileBase64Data = base64_encode($originalFileData);
$originalFileBase64DataLength = strlen($originalFileBase64Data) - 1;
$originalFileBase64DataArray = str_split($originalFileBase64Data);
$encryptedData = NULL;
$encryptedDataKey = NULL;
for ($i = 0; $i <= $originalFileBase64DataLength; $i++) {
$randKey = rand(0, sizeOf(self::$charSet) - 1);
$arrayKey = array_search($originalFileBase64DataArray[$i], self::$charSet);
if($randKey > $arrayKey) {
$str = '-' . ($randKey - $arrayKey);
} elseif($randKey < $arrayKey) {
$str = ($randKey + $arrayKey);
} else {
$str = $randKey;
}
$encryptedData .= self::$charSet[$randKey];
$encryptedDataKey .= $str. ';';
}
$encryptedDataString = $encryptedData;
$encryptedDataKeyString = $encryptedDataKey;
if(!self::existsFile($keyFilePath)) {
file_put_contents($keyFilePath, $encryptedDataKeyString);
}
if(!self::existsFile($encryptedFilePath)) {
file_put_contents($encryptedFilePath, $encryptedDataString);
}
return 'OK';
} else {
return 'Source file not exists';
}
} else {
return 'Encrypted data already exists';
}
}
public static function decryptFile($encryptedFilePath, $keyFilePath, $decryptedFilePath)
{
$keyFileData = self::existsFile($keyFilePath);
$encryptedFileData = self::existsFile($encryptedFilePath);
$encryptedFileDataLength = strlen($encryptedFileData) - 1;
if($encryptedFileData && $keyFileData) {
$encryptedFileDataArray = str_split($encryptedFileData);
$keyFileDataArray = explode(';', $keyFileData);
$decryptedData = NULL;
for ($i = 0; $i <= $encryptedFileDataLength; $i++) {
$poziciaaktualneho = array_search($encryptedFileDataArray[$i], self::$charSet);
$poziciasifrovana = $keyFileDataArray[$i];
if($poziciasifrovana < 0) {
$move = $poziciasifrovana + $poziciaaktualneho;
} elseif($poziciasifrovana > 0) {
$move = $poziciasifrovana - $poziciaaktualneho;
} else {
$move = '0';
}
$decryptedData .= self::$charSet[$move];
}
if(!self::existsFile($decryptedFilePath)) {
file_put_contents($decryptedFilePath, base64_decode($decryptedData));
return 'OK';
} else {
return 'Decrypted data already exists';
}
}
}
private static function existsFile($filePath)
{
$fileData = #file_get_contents($filePath);
if($fileData) {
return $fileData;
}
return FALSE;
}
}
$originalFilePath = 'original.jpg';
$keyFilePath = 'Otp_Key_' . $originalFilePath;
$encryptedFilePath = 'Otp_Data_' . $originalFilePath;
$decryptedFilePath = 'Otp_Decrypted_' . $originalFilePath;
echo Otp::encryptFile($originalFilePath, $encryptedFilePath, $keyFilePath);
echo Otp::decryptFile($encryptedFilePath, $keyFilePath, $decryptedFilePath);

Answer 1

The problem seems to be only happening when $poziciaaktualneho is equal to $poziciasifrovana and so by adding another if statement on line 78 to check for this and instead set $move equal to $poziciasifrovana I was able to fix the problem. The below script should work:
final class Otp
{
private static $charSet = array('+','/','0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K','L',
'M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r',
's','t','u','v','w','x','y','z');
public static function encryptFile($originalFilePath, $encryptedFilePath, $keyFilePath)
{
if(!self::existsFile($keyFilePath) || !self::existsFile($encryptedFilePath)) {
if($originalFileData = self::existsFile($originalFilePath)) {
$originalFileBase64Data = base64_encode($originalFileData);
$originalFileBase64DataLength = strlen($originalFileBase64Data) - 1;
$originalFileBase64DataArray = str_split($originalFileBase64Data);
$encryptedData = NULL;
$encryptedDataKey = NULL;
for ($i = 0; $i <= $originalFileBase64DataLength; $i++) {
$randKey = rand(0, sizeOf(self::$charSet) - 1);
$arrayKey = array_search($originalFileBase64DataArray[$i], self::$charSet);
if($randKey > $arrayKey) {
$str = '-' . ($randKey - $arrayKey);
} elseif($randKey < $arrayKey) {
$str = ($randKey + $arrayKey);
} else {
$str = $randKey;
}
$encryptedData .= self::$charSet[$randKey];
$encryptedDataKey .= $str. ';';
}
$encryptedDataString = $encryptedData;
$encryptedDataKeyString = $encryptedDataKey;
if(!self::existsFile($keyFilePath)) {
file_put_contents($keyFilePath, $encryptedDataKeyString);
}
if(!self::existsFile($encryptedFilePath)) {
file_put_contents($encryptedFilePath, $encryptedDataString);
}
return 'OK';
} else {
return 'Source file not exists';
}
} else {
return 'Encrypted data already exists';
}
}
public static function decryptFile($encryptedFilePath, $keyFilePath, $decryptedFilePath)
{
$keyFileData = self::existsFile($keyFilePath);
$encryptedFileData = self::existsFile($encryptedFilePath);
$encryptedFileDataLength = strlen($encryptedFileData) - 1;
if($encryptedFileData && $keyFileData) {
$encryptedFileDataArray = str_split($encryptedFileData);
$keyFileDataArray = explode(';', $keyFileData);
$decryptedData = NULL;
for ($i = 0; $i <= $encryptedFileDataLength; $i++) {
$poziciaaktualneho = array_search($encryptedFileDataArray[$i], self::$charSet);
$poziciasifrovana = $keyFileDataArray[$i];
if ($poziciasifrovana == $poziciaaktualneho) {
$move = $poziciasifrovana;
} elseif($poziciasifrovana < 0) {
$move = $poziciasifrovana + $poziciaaktualneho;
} elseif($poziciasifrovana > 0) {
$move = $poziciasifrovana - $poziciaaktualneho;
} else {
$move = '0';
}
$decryptedData .= self::$charSet[$move];
}
if(!self::existsFile($decryptedFilePath)) {
file_put_contents($decryptedFilePath, base64_decode($decryptedData));
return 'OK';
} else {
return 'Decrypted data already exists';
}
}
}
private static function existsFile($filePath)
{
$fileData = #file_get_contents($filePath);
if($fileData) {
return $fileData;
}
return FALSE;
}
}
$originalFilePath = 'original.jpg';
$keyFilePath = 'Otp_Key_' . $originalFilePath;
$encryptedFilePath = 'Otp_Data_' . $originalFilePath;
$decryptedFilePath = 'Otp_Decrypted_' . $originalFilePath;
echo Otp::encryptFile($originalFilePath, $encryptedFilePath, $keyFilePath);
echo Otp::decryptFile($encryptedFilePath, $keyFilePath, $decryptedFilePath);
Warning: I would not recommend using my solution in an enterprise setting if at all since I do not know why this fixes your script or what was
originally wrong with it and it is most likely not air tight.