Php encrypt file with password

I did a series of research on this topic, but unfortunately I couldn't find a perfect way to encrypt and decrypt files in PHP. Which mean what I'm trying to do is find some way to encrypt & decrypt my items without worry of cracker knew my algorithm. If some algorithm that need to secrete & hide, it can't solve my problems while once the logic shared through anywhere, or they broke into my server and get the source file, then it should be some way to decrypt it using the same decryption algorithm. Previously I found several great posts on StackOverFlow website, but it still couldn't answer my question.

The best way to encrypt password of the world, from what I conclude through reading. Blowfish encryption. It's one way hashing algorithm with 1000's times iteration which make cracker need 7 years to decrypt by using the same specification GPU.

Obviously, this makes it impossible to decrypt while it's one-way hashing.

1. How do you use bcrypt for hashing passwords in PHP?
2. Why do salts make dictionary attacks 'impossible'?

The best way to encrypt and decrypt password in PHP, as this question quote as it is. Refer to what I found through the web, sha1 and md5 both are cracked & broken algorithm, even we change the algorithm from

$encrypted = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, md5($key), $string, MCRYPT_MODE_CBC, md5(md5($key))));

To

$encrypted = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, sha1(md5($key)), $string, MCRYPT_MODE_CBC, sha1(md5(md5($key)))));

Are not it's just increasing the toughness to decrypt it but still crack-able while just time issue ?

1. Best way to use PHP to encrypt and decrypt passwords?

I'm thinking of using our server processor / harddisc GUID to generate the salt and encrypt the password.

It's still some stupid way to do while cracker got the access to the server and they can just use PHP to echo the GUID and do the decryption. Or if it works, a few years later my website will be in trouble. The reason is harddisc, processor never last forever. When the time my processor or harddisc down, it's a time when my website down and lost all the credential.

Update

Found this question which doing with blowfish for decryption in PHP. Is it solving the question of finding secured way to encrypt and hard to decrypt by others ?

1. How to decrypt using Blowfish algorithm in php?

Can anyone please suggest on how should I overcome this issue ? Thanks.

asked Aug 20, 2012 at 4:16

14

Checkout this well documented article A reversible password encryption routine for PHP, intended for those PHP developers who want a password encryption routine that is reversible.

Even though this class is intended for password encryption, you can use it for encryption/decryption of any text.

function encryption_class() {
    $this->errors = array();

    // Each of these two strings must contain the same characters, but in a different order.
    // Use only printable characters from the ASCII table.
    // Do not use single quote, double quote or backslash as these have special meanings in PHP.
    // Each character can only appear once in each string.
    $this->scramble1 = '! #$%&()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[]^_`abcdefghijklmnopqrstuvwxyz{|}~';
    $this->scramble2 = 'f^jAE]okIOzU[2&q1{3`h5w_794p@6s8?BgP>dFV=m Dscramble1) <> strlen($this->scramble2)) {
        trigger_error('** SCRAMBLE1 is not same length as SCRAMBLE2 **', E_USER_ERROR);
    } // if

    $this->adj = 1.75;  // this value is added to the rolling fudgefactors
    $this->mod = 3;     // if divisible by this the adjustment is made negative
}

Caution:

If you are using PHP version >= 5.3.3, then you have to change the class name from encryption_class to __construct

Reason:

As of PHP 5.3.3, methods with the same name as the last element of a namespaced class name will no longer be treated as constructor.

Usage:

$crypt = new encryption_class();

$crypt->setAdjustment(1.75); // 1st adjustment value (optional)
$crypt->setModulus(3); // 2nd adjustment value (optional)

/**
 * 
 * @param string $key - Your encryption key
 * @param string $sourceText - The source text to be encrypted
 * @param integer $encLen - positive integer indicating the minimum length of encrypted text
 * @return string - encrypted text
 */
$encrypt_result = $crypt->encrypt($key, $sourceText, $encLen);

/**
 * 
 * @param string $key - Your encryption key (same used for encryption)
 * @param string $encrypt_result - The text to be decrypted
 * @return string - decrypted text
 */
$decrypt_result = $crypt->decrypt($key, $encrypt_result);

Update:

Above class is not intended for encrypting files, but you can!!!

1. base64_encode your source text (file contents)
2. for actual encryption, apply above enc/dec class over base64-encoded text
3. for decryption, apply above enc/dec class over actually encrypted text
4. base64_decode will give you the actual file contents (you can save a copy of file with this content)

I've encrypted an image, decrypted back and saved to a new file!!! checkout the code.

//class for encrypt/decrypt routines 
require 'class.encryption.php';

//configuring your security levels
$key = 'This is my secret key; with symbols (@$^*&/!#_+), cool eh?!!! :)';
$adjustment = 1.75;
$modulus = 2;

//customizing
$sourceFileName = 'source-image.png';
$destFileName = 'dest-image.png';
$minSpecifiedLength = 512;

//base64 encoding file contents, to get all characters in our range
//binary too!!!
$sourceText = base64_encode(file_get_contents($sourceFileName));

$crypt = new encryption_class();
$crypt->setAdjustment($adjustment); //optional
$crypt->setModulus($modulus); //optional

//encrypted text
$encrypt_result = $crypt->encrypt($key, $sourceText, $minSpecifiedLength);

//receive initial file contents after decryption
$decrypt_result = base64_decode($crypt->decrypt($key, $encrypt_result));

//save as new file!!!
file_put_contents($destFileName, $decrypt_result);

answered Aug 24, 2012 at 7:06

rajukoyilandyrajukoyilandy

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4

Bear in mind that, in order to crack passwords, a hacker would have to have access to the encrypted passwords in the first place. In order to do that they would have to compromise the server's security, which should be impossible if the site is coded correctly (proper escaping or prepared statements).

One of the strongest yet simplest forms of encryption is XOR, however it is entirely dependent on the key. If the key is the same length as the encoded text, then it is completely unbreakable without that key. Even having the key half the length of the text is extremely unlikely to be broken.

In the end, though, whatever method you choose is secured by your FTP/SSH/whatever password that allows you to access the server's files. If your own password is compromised, a hacker can see everything.

answered Aug 20, 2012 at 4:22

Your question leads to two different answers. It's an important difference, whether you need to decrypt the data later (like files), or if you can use a one way hash (for passwords).

One-Way-Hash

If you do not need to decrypt your data (passwords), you should use a hash function. This is safer, because even if an attacker has control over your server and your database, he should not be able to retrieve the original password. Since users often use their password for several websites, at least he doesn't gain access to other sites as well.

As you already stated, one of the most recommended hash functions today, is bcrypt. Despite it's origin in the blowfish algorithm, it is in fact a hash function (not encryption). Bcrypt was designed especially to hash passwords, and is therefore slow (needs computing time). It's recommended to use a well established library like phpass, and if you want to understand how to implement it, you can read this article, where i tried to explain the most important points.

Encryption

If you need to decrypt your data later (files), you cannot prevent, that an attacker with control over your server, can decrypt the files as well (after all the server has to be able to decrypt it). All adds up to the question of where to store the secret key. The only thing you can do, is to make it harder to get the key.

That means, if you store the key in a file, it should be outside the http root directory, so it can on no account be accessed from the internet. You could store it on a different server, so the attacker would need control over both servers, though then you face the problem of the secure communication between the servers. In every case, you can make theft harder, but you cannot prevent it completely.

Depending on your scenario, you could encrypt the files locally on your computer, and only store the encrypted files on the server. The server would not be able to decrypt the files on it's own then, so they are safe.

answered Aug 25, 2012 at 9:16

martinstoecklimartinstoeckli

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So you already know about salting and hashing, but you can also "stretch" your passwords, where instead of just hashing each password once, you hash it several thousand times. This will slow down brute force attacks and increase the lifespan of your hashing algorithm. Interestingly it works by intentionally slowing down your server...

What I would recommend is writing your own custom hash function. First, you add salt to the password, then you pick a hash algorithm (say sha512, or perhaps a newer algorithm that is designed to be inefficient for this very purpose) and hash it, say, 10,000 times, then store it in the database. And as you already know, when a user logs in, instead of reversing the hash, you simply run their input through the same algorithm and see if it matches.

The beauty of writing your own hash function is that when it comes time to update your hash algorithm because the old one has become vulnerable to brute force attacks, all you have to do is add to your hash function, taking the result of the old hash algorithm, re-salting it, and hashing it again using your new algorithm. You can use whatever hash algorithm is considered secure at the time. Then, you can simply re-hash every password already stored in your database with the new part of your hash function, thus ensuring backwards compatibility. Depending on how many users you have and how fast your server is, it might only take a couple of seconds to perform this update.

There is still a vulnerability, however. If a hacker has an old copy of your database and cracks it, he still knows the passwords of any users who haven't changed their passwords yet. The only way around this is to require your users to occasionally change their passwords, which may or may not be suitable for your site depending on the nature of the information it contains. Some security professionals suggest that users only change their passwords if they are compromised because if the system makes it too difficult to manage passwords, they will begin doing insecure things like keeping their passwords under their keyboards, which for some organizations is a bigger threat than having users that never change their passwords. If your website is a forum or review site or something of that nature, you should consider how much users have to lose by having their account hacked, how easy it is to restore their data to the way it was before it was hacked, and whether they will consider your site worth updating their password for if your password policy is too annoying.

One possible hash function:

function the_awesomest_hash($password)
{
    $salt1 = "awesomesalt!";
    $password = $salt1 . $password;
    for($i = 0; $i < 10000; $i++)
    {
        $password = hash('sha512', $password);
    }
    // Some time has passed, and you have added to your hash function
    $salt2 = "niftysalt!";
    $password = $salt2 . $password;
    for($i = 0; $i < 10000; $i++)
    {
        $password = hash('futuresuperhash2024', $password);
    }
    return $password;
}

Now, in order to update all the passwords already in your database, you would run them through this function:

function update_hash($password)
{
    // This is the last part of your the_awesomest_hash() function
    $salt2 = "niftysalt!";
    $password = $salt2 . $password;
    for($i = 0; $i < 10000; $i++)
    {
        $password = hash('futuresuperhash2024', $password);
    }
    return $password;
}

I like to write my own hash functions because it's easier to keep track of what exactly is happening for when it comes time to update them.

answered Aug 26, 2012 at 19:03

Adam11Adam11

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After some study of PHP, particularly the random number generation, the only way to securely encrypt with PHP is by using an OpenSSL wrapper. Especially the creators of mcrypt are a bunch of morons, just look at the example of not how to perform cryptography in their sample:

$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB);
$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
$key = "This is a very secret key";
$text = "Meet me at 11 o'clock behind the monument.";
echo strlen($text) . "\n";

$crypttext = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $text, MCRYPT_MODE_ECB, $iv);
echo strlen($crypttext) . "\n";

Note that by default MCRYPT_RAND is not seeded well. Furthermore, there is at least about 5 mistakes in above code alone, and they won't fix it.

[EDIT] See below for an ammended sample. Note that this sample is not very safe either (as explained above). Furthermore normally you should not encrypt passwords...

# the key should be random binary, use scrypt, bcrypt or PBKDF2 to convert a string into a key
# key is specified using hexadecimals
$key = pack('H*', "bcb04b7e103a0cd8b54763051cef08bc55abe029fdebae5e1d417e2ffb2a00a3");
echo "Key size (in bits): " . $key_size * 8 . "\n";
$plaintext = "This string was AES-256 / CBC / ZeroBytePadding encrypted.";
echo "Plain text: " . $plain_text . "\n";
$ciphertext_base64 = encryptText($key, $plaintext);
echo  $ciphertext_base64 . "\n";


function encryptText(string $key_hex, string $plaintext) {

    # --- ENCRYPTION ---


    # show key size use either 16, 24 or 32 byte keys for AES-128, 192 and 256 respectively
    $key_size =  strlen($key);


    # 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);

    # use an explicit encoding for the plain text
    $plaintext_utf8 = utf8_encode($plaintext);

    # 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_utf8, 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);

    return $ciphertext_base64;
}


# === 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_utf8_dec = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $ciphertext_dec, MCRYPT_MODE_CBC, $iv_dec);

echo  $plaintext_utf8_dec . "\n";

answered Aug 20, 2012 at 12:38

Maarten BodewesMaarten Bodewes

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3

So far i know the best way to save password is with salted hash like used in joomla. You can also add extra keys to md5 hash along with traditional base64.I wrote a script like that sometime ago, tried to find it but can't.

Joomla uses salted md5 passwords. Take the hashed password you gave: 30590cccd0c7fd813ffc724591aea603:WDmIt53GwY2X7TvMqDXaMWJ1mrdZ1sKb

If your password was say 'password', then: md5('passwordWDmIt53GwY2X7TvMqDXaMWJ1mrdZ1sKb') = 30590cccd0c7fd813ffc724591aea603

So, take your password. Generate a random 32 character string. Compute the md5 of the password concatenated with the random string. Store the md5 result plus a : plus the random 32 character string in the database.

answered Aug 24, 2012 at 21:03

1

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