[php] How to encrypt/decrypt data in php?

I'm currently a student and I'm studying PHP, I'm trying to make a simple encrypt/decrypt of data in PHP. I made some online research and some of them were quite confusing(at least for me).

Here's what I'm trying to do:

I have a table consisting of these fields (UserID,Fname,Lname,Email,Password)

What I want to have is have the all fields encrypted and then be decrypted(Is it possible to use sha256 for encryption/decryption, if not any encryption algorithm)

Another thing I want to learn is how to create a one way hash(sha256) combined with a good "salt". (Basically I just want to have a simple implementation of encryption/decryption, hash(sha256)+salt) Sir/Ma'am, your answers would be of great help and be very much appreciated. Thank you++

Answer Background and Explanation

To understand this question, you must first understand what SHA256 is. SHA256 is a Cryptographic Hash Function. A Cryptographic Hash Function is a one-way function, whose output is cryptographically secure. This means it is easy to compute a hash (equivalent to encrypting data), but hard to get the original input using the hash (equivalent to decrypting the data). Since using a Cryptographic hash function means decrypting is computationally infeasible, so therefore you cannot perform decryption with SHA256.

What you want to use is a two-way function, but more specifically, a Block Cipher. A function that allows for both encryption and decryption of data. The functions mcrypt_encrypt and mcrypt_decrypt by default use the Blowfish algorithm. PHP's use of mcrypt can be found in this manual. A list of cipher definitions to select the cipher mcrypt uses also exists. A wiki on Blowfish can be found at Wikipedia. A block cipher encrypts the input in blocks of known size and position with a known key, so that the data can later be decrypted using the key. This is what SHA256 cannot provide you.

Code

$key = 'ThisIsTheCipherKey';

$ciphertext = mcrypt_encrypt(MCRYPT_BLOWFISH, $key, 'This is plaintext.', MCRYPT_MODE_CFB);

$plaintext = mcrypt_decrypt(MCRYPT_BLOWFISH, $key, $encrypted, MCRYPT_MODE_CFB);

It took me quite a while to figure out, how to not get a false when using openssl_decrypt() and get encrypt and decrypt working.

    // cryptographic key of a binary string 16 bytes long (because AES-128 has a key size of 16 bytes)
    $encryption_key = '58adf8c78efef9570c447295008e2e6e'; // example
    $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length('aes-256-cbc'));
    $encrypted = openssl_encrypt($plaintext, 'aes-256-cbc', $encryption_key, OPENSSL_RAW_DATA, $iv);
    $encrypted = $encrypted . ':' . base64_encode($iv);

    // decrypt to get again $plaintext
    $parts = explode(':', $encrypted);
    $decrypted = openssl_decrypt($parts[0], 'aes-256-cbc', $encryption_key, OPENSSL_RAW_DATA, base64_decode($parts[1])); 

If you want to pass the encrypted string via a URL, you need to urlencode the string:

    $encrypted = urlencode($encrypted);

To better understand what is going on, read:

• http://blog.turret.io/the-missing-php-aes-encryption-example/
• http://thefsb.tumblr.com/post/110749271235/using-opensslendecrypt-in-php-

To generate 16 bytes long keys you can use:

    $bytes = openssl_random_pseudo_bytes(16);
    $hex = bin2hex($bytes);

To see error messages of openssl you can use: echo openssl_error_string();

Hope that helps.

     function my_simple_crypt( $string, $action = 'e' ) {
        // you may change these values to your own
        $secret_key = 'my_simple_secret_key';
        $secret_iv = 'my_simple_secret_iv';

        $output = false;
        $encrypt_method = "AES-256-CBC";
        $key = hash( 'sha256', $secret_key );
        $iv = substr( hash( 'sha256', $secret_iv ), 0, 16 );

        if( $action == 'e' ) {
            $output = base64_encode( openssl_encrypt( $string, $encrypt_method, $key, 0, $iv ) );
        }
        else if( $action == 'd' ){
            $output = openssl_decrypt( base64_decode( $string ), $encrypt_method, $key, 0, $iv );
        }

        return $output;
    }

Here is an example using openssl_encrypt

//Encryption:
$textToEncrypt = "My Text to Encrypt";
$encryptionMethod = "AES-256-CBC";
$secretHash = "encryptionhash";
$iv = mcrypt_create_iv(16, MCRYPT_RAND);
$encryptedText = openssl_encrypt($textToEncrypt,$encryptionMethod,$secretHash, 0, $iv);

//Decryption:
$decryptedText = openssl_decrypt($encryptedText, $encryptionMethod, $secretHash, 0, $iv);
print "My Decrypted Text: ". $decryptedText;

I'm think this has been answered before...but anyway, if you want to encrypt/decrypt data, you can't use SHA256

//Key
$key = 'SuperSecretKey';

//To Encrypt:
$encrypted = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, 'I want to encrypt this', MCRYPT_MODE_ECB);

//To Decrypt:
$decrypted = mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, $encrypted, MCRYPT_MODE_ECB);