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Encryption


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<?php
    # --- ENCRYPTION ---

    # The key should be a random binary. Use scrypt, bcrypt or
    # PBKDF2 to convert a string into a key.
    # The key is specified using hexadecimal.
    $key = pack('H*', "bcb04b7e103a0cd8b54763051cef08bc". "55abe029fdebae5e1d417e2ffb2a00a3");
    
    # This shows the key size. Use either 16-, 24- or 32- byte 
    # keys for AES-128, 192 and 256 respectively
    $key_size =  strlen($key);
    echo "Key size: " . $key_size . "\n";
    
    $plaintext = "This string was AES-256 / CBC / ". "ZeroBytePadding encrypted.";

    # create a random IV to use with CBC encoding
    $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
    $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
    
    # creates a cipher text compatible with AES (Rijndael 
    # block size = 128) to keep the text confidential 
    # only suitable for encoded input that never ends with 
    # value 00h (because of default zero padding)
    $ciphertext = mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $plaintext, MCRYPT_MODE_CBC, $iv);

    # prepend the IV for it to be available for decryption
    $ciphertext = $iv . $ciphertext;
    
    # encode the resulting cipher text so it can be 
    # represented by a string
    $ciphertext_base64 = base64_encode($ciphertext);

    echo  $ciphertext_base64 . "\n";

    # === WARNING ===
    # Resulting cipher text has no integrity or authenticity 
    # added and is not protected against padding oracle 
    # attacks.
    
    # --- DECRYPTION ---
    
    $ciphertext_dec = base64_decode($ciphertext_base64);
    
    # retrieves the IV, iv_size should be created using 
    # mcrypt_get_iv_size()
    $iv_dec = substr($ciphertext_dec, 0, $iv_size);
    
    # retrieves the cipher text (everything except the 
    # $iv_size in the front)
    $ciphertext_dec = substr($ciphertext_dec, $iv_size);

    # may remove 00h valued characters from end of plain text
    $plaintext_dec = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $ciphertext_dec, MCRYPT_MODE_CBC, $iv_dec);
    
    echo  $plaintext_dec . "\n";
?>
/* (courtesy of http://my1.php.net/manual/en/function.mcrypt-encrypt.php) */