[edit] Last updated: Fri, 25 May 2012

openssl_encrypt

(PHP 5 >= 5.3.0)

openssl_encrypt — Encrypts data

Description

string openssl_encrypt ( string $data , string $method , string $password [, bool $raw_output = false [, string $iv = "" ]] )

Encrypts given data with given method and key, returns a raw or base64 encoded string

Warning

This function is currently not documented; only its argument list is available.

Parameters

data: The data.
method: The cipher method.
password: The password.
raw_output: Setting to TRUE will return as raw output data, otherwise the return value is base64 encoded.
iv: A non-NULL Initialization Vector.

Return Values

Returns the encrypted string on success or FALSE on failure.

Errors/Exceptions

Emits an E_WARNING level error if an unknown cipher algorithm is passed in via the method parameter.

Emits an E_WARNING level error if an empty value is passed in via the iv parameter.

Changelog

Version	Description
5.3.3	The `iv` parameter was added.


Many users give up with handilng problem when openssl command line tool cant decrypt php openssl encrypted file which is encrypted with openssl_encrypt function.



For example how beginner is encrypting data:



<?php



$string = 'It works ? Or not it works ?';

$pass = '1234';

$method = 'aes128';



file_put_contents ('./file.encrypted', openssl_encrypt ($string, $method, $pass));



?>



And then how beginner is trying to decrypt data from command line:



# openssl enc -aes-128-cbc -d -in file.encrypted -pass pass:123



Or even if he/she determinates that openssl_encrypt output was base64 and tries:



# openssl enc -aes-128-cbc -d -in file.encrypted -base64 -pass pass:123



Or even if he determinates that base64 encoded file is represented in one line and tries:



# openssl enc -aes-128-cbc -d -in file.encrypted -base64 -A -pass pass:123



Or even if he determinates that IV is needed and adds some string iv as encryption function`s fourth parameter and than adds hex representation of iv as parameter in openssl command line :



# openssl enc -aes-128-cbc -d -in file.encrypted -base64 -pass pass:123 -iv -iv 31323334353637383132333435363738



Or even if he determinates that aes-128 password must be 128 bits there fore 16 bytes and sets $pass = '1234567812345678' and tries:



# openssl enc -aes-128-cbc -d -in file.encrypted -base64 -pass pass:1234567812345678 -iv -iv 31323334353637383132333435363738



All these troubles will have no result in any case.



BECAUSE THE PASSWORD PARAMETER DOCUMENTED HERE IS NOT THE PASSWORD.



It means that the password parameter of the function is not the same string used as [-pass pass:] parameter with openssl cmd tool for file encryption decryption.



IT IS THE KEY !



And now how to correctly encrypt data with php openssl_encrypt and how to correctly decrypt it from openssl command line tool.



<?php



    function strtohex($x) 

    {

        $s='';

        foreach (str_split($x) as $c) $s.=sprintf("%02X",ord($c));

        return($s);

    } 

    

    $source = 'It works !';



    $iv = "1234567812345678";

    $pass = '1234567812345678';

    $method = 'aes-128-cbc';



    echo "\niv in hex to use: ".strtohex ($iv);

    echo "\nkey in hex to use: ".strtohex ($pass);

    echo "\n";



    file_put_contents ('./file.encrypted',openssl_encrypt ($source, $method, $pass, true, $iv));



    $exec = "openssl enc -".$method." -d -in file.encrypted -nosalt -nopad -K ".strtohex($pass)." -iv ".strtohex($iv);



    echo 'executing: '.$exec."\n\n";

    echo exec ($exec);

    echo "\n";



?>



IV and Key parameteres passed to openssl command line must be in hex representation of string.



The correct command for decrypting is:



# openssl enc -aes-128-cbc -d -in file.encrypted -nosalt -nopad -K 31323334353637383132333435363738 -iv 31323334353637383132333435363738



As it has no salt has no padding and by setting functions third parameter we have no more base64 encoded file to decode. The command will echo that it works...



: /

public at grik dot net 01-Aug-2010 11:25


In 5.3.3 they added a new parameter, string $iv (initialization vector)

Real parameters are:

string openssl_encrypt ( string $data , string $method , string $password, bool $raw_output = false, string $iv )



If $iv is missing, a warning is issued: "Using an empty Initialization Vector (iv) is potentially insecure and not recommended".



If $iv is too short, another warning: 

"IV passed is only 3 bytes long, cipher expects an IV of precisely 8 bytes, padding with \0"



same IV should be used in openssl_decrypt()

public at grik dot net 25-Dec-2009 02:54


The list of methods for this function can be obtained with openssl_get_cipher_methods();

The password can be encrypted with the openssl_private/public_encrypt()

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