note 120141 added to function.openssl-encrypt

PHP lacks a build-in function to encrypt and decrypt large files. openssl_encrypt() can be used to encrypt strings, but loading a huge file into memory is a bad idea. So we have to write a userland function doing that. This example uses the symmetric AES-128-CBC algorithm to encrypt smaller chunks of a large file and writes them into another file. # Encrypt Files <?php /** * Define the number of blocks that should be read from the source file for each chunk. * For 'AES-128-CBC' each block consist of 16 bytes. * So if we read 10,000 blocks we load 160kb into memory. You may adjust this value * to read/write shorter or longer chunks. */ define('FILE_ENCRYPTION_BLOCKS', 10000); /** * Encrypt the passed file and saves the result in a new file with ".enc" as suffix. * * @param string $source Path to file that should be encrypted * @param string $key The key used for the encryption * @param string $dest File name where the encryped file should be written to. * @return string|false Returns the file name that has been created or FALSE if an error occured */ function encryptFile($source, $key, $dest) { $key = substr(sha1($key, true), 0, 16); $iv = openssl_random_pseudo_bytes(16); $error = false; if ($fpOut = fopen($dest, 'w')) { // Put the initialzation vector to the beginning of the file fwrite($fpOut, $iv); if ($fpIn = fopen($source, 'rb')) { while (!feof($fpIn)) { $plaintext = fread($fpIn, 16 * FILE_ENCRYPTION_BLOCKS); $ciphertext = openssl_encrypt($plaintext, 'AES-128-CBC', $key, OPENSSL_RAW_DATA, $iv); // Use the first 16 bytes of the ciphertext as the next initialization vector $iv = substr($ciphertext, 0, 16); fwrite($fpOut, $ciphertext); } fclose($fpIn); } else { $error = true; } fclose($fpOut); } else { $error = true; } return $error ? false : $dest; } ?> # Decrypt Files To decrypt files that have been encrypted with the above function you can use this function. <?php /** * Dencrypt the passed file and saves the result in a new file, removing the * last 4 characters from file name. * * @param string $source Path to file that should be decrypted * @param string $key The key used for the decryption (must be the same as for encryption) * @param string $dest File name where the decryped file should be written to. * @return string|false Returns the file name that has been created or FALSE if an error occured */ function decryptFile($source, $key, $dest) { $key = substr(sha1($key, true), 0, 16); $error = false; if ($fpOut = fopen($dest, 'w')) { if ($fpIn = fopen($source, 'rb')) { // Get the initialzation vector from the beginning of the file $iv = fread($fpIn, 16); while (!feof($fpIn)) { // we have to read one block more for decrypting than for encrypting $ciphertext = fread($fpIn, 16 * (FILE_ENCRYPTION_BLOCKS + 1)); $plaintext = openssl_decrypt($ciphertext, 'AES-128-CBC', $key, OPENSSL_RAW_DATA, $iv); // Use the first 16 bytes of the ciphertext as the next initialization vector $iv = substr($ciphertext, 0, 16); fwrite($fpOut, $plaintext); } fclose($fpIn); } else { $error = true; } fclose($fpOut); } else { $error = true; } return $error ? false : $dest; } ?> Source: http://stackoverflow.com/documentation/php/5794/cryptography/25499/ ---- Server IP: 72.52.91.14 Probable Submitter: 80.87.117.30 ---- Manual Page -- http://php.net/manual/en/function.openssl-encrypt.php Edit -- https://master.php.net/note/edit/120141 Del: integrated -- https://master.php.net/note/delete/120141/integrated Del: useless -- https://master.php.net/note/delete/120141/useless Del: bad code -- https://master.php.net/note/delete/120141/bad+code Del: spam -- https://master.php.net/note/delete/120141/spam Del: non-english -- https://master.php.net/note/delete/120141/non-english Del: in docs -- https://master.php.net/note/delete/120141/in+docs Del: other reasons-- https://master.php.net/note/delete/120141 Reject -- https://master.php.net/note/reject/120141 Search -- https://master.php.net/manage/user-notes.php