mcrypt help

[mhalloran]

Hello,

I've been having trouble finding a solution for this scenario. I want to encrypt some sensitive data using a key (public key?) right before it goes into the database. Because this key will be stored on the server, I want have a different key that must be entered in protected SSL area in order to view the sensitive data.

Right now I just use MySQL's encode/decode functions but I don't like having the key stored on-line in case someone manages to break into the server.

Does anyone have some code or good link that will help me set up a multiple key encryption system?

• Mark

[dpearre]

i use gpg -- it took forever to figure out how to use it along with php (an o'reily book was essential). if it's installed on your server, i think it's a pretty effective way to store sensitive data.

function gpg_encrypt($msg, $sender, $recipient){

$gpg_path 	= '/usr/local/bin/gpg';
$home_dir   = '/home/myhomedir';

$msg 		= escapeshellarg($msg);
$sender     = escapeshellarg($sender);
$recipient  = escapeshellarg($recipient);
$user_env   = 'web';

$cmd 		=  "echo $msg | HOME=$home_dir USER=$user_env $gpg_path " .
               "--quiet --no-secmem-warning --encrypt --sign --armor " . 
               "--recipient $recipient --local-user $sender";

$output		= shell_exec($cmd." 2>&1");	
return $output;
}


function gpg_decrypt($msg, $passphrase){

$gpg_path 	= '/usr/local/bin/gpg';
$home_dir   = '/home/myhomedir/.gnupg';
$filename   = uniqid("");
$tmp_file	= tempnam("/home/myhomedir/tmp",$filename);
$handle		= fopen($tmp_file,"w");

fwrite($handle,$msg);
fclose($handle);

$passphrase = escapeshellarg($passphrase);

$cmd		= "echo $passphrase | $gpg_path " .
    		  "--quiet --no-secmem-warning --homedir $home_dir " .
   			  "--batch --no-tty --passphrase-fd 0 --decrypt '$tmp_file'";		  

$output		= shell_exec($cmd." 2>&1");

// delete first 4 lines

$output		= eregi_replace("^([^\n]*\n){3}","",$output);

$output     = nl2br($output);
unlink($tmp_file);
return $output;
}

you can test it using this script:

$secret_message = "This is a secret message";

$encrypted		= gpg_encrypt($secret_message, "[e-mail]", "[e-mail]");
$un_encrypted	= gpg_decrypt($encrypted, "supersecretpassphrase");

echo "<p>encryped:<br />$encrypted</p>";
echo "<p>un_encrypted:<br />$un_encrypted</p>";

where 'supersecretpassphrase' is [e-mail]'s gpg passphrase.

make sure there's a world readable/writable "tmp" directory in your home directory. look to my other recent post on what the .gnupg permissions should be. let me know if you need help setting up the gpg keys as well.