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Daniel Brown wrote:
> On Dec 19, 2007 2:41 AM, Keith Spiller <larentium@xxxxxxxxxxxx> wrote:
>> Ok I've done some research and some thinking. What about storing orders in
>> the database (product info and customer info) and then using GnuPG or PGP to
>> send the credit card info to the merchant? This way the credit card
>> information is not stored on the server or in the database but only in
>> printed format by the merchant. Since my client processes all of the credit
>> card orders by hand this seems like an ideal solution.
>
> I had a client that did offline (manual) processing of credit card
> orders as well. With liability issues and the problems that others
> have already pointed out, storing the credit card information was not
> an option, yet my client still needed some way of having the data
> available offline.
>
> Consider the following:
>
> ISSUER LENGTH
> Diner's Club/Carte Blanche 14
> American Express 15
> VISA 13 or 16
> MasterCard 16
> Discover 16
>
> Security checks aside (like making sure they selected the type of
> card and that it matched the algorithm - VISA beginning with 4 and
> being strlen($_POST['cardnum']) == 13 or 16, MasterCard being 16,
> beginning with 51xx to 55xx, et cetera), I then had a hybrid of
> storage and delivery.
>
> Mail the first <? rand(4,6); ?> digits to the sales email
> address(es) on file. Three addresses on two domains were used for
> redundancy in this case. Store the remaining digits in the database.
> You could write your own encryption algorithm or use one that is
> publicly-available and reversible (Blowfish is what I was using, at
> 128, key length of 56 lower ASCII characters, padded with 7 on the key
> and four on the output - MD5, SHA1, et al are NOT options here).
>
> The sales department then received the first digits of the credit
> card number via email, which stated it was an order key. Again, in my
Using the order number as the key is bad practice. Here is a random key
generator that you could use for your public/private keys and still use
the blowfish cipher as your method of encrypting:
<?PHP
function ReadFolder( $folder )
{
if( ( empty( $folder ) ) || ( !is_dir( $folder ) ) ) {
$rand_image = GenerateError( "Couldn't open directory" );
} else {
$rand_image = array();
if( $handle = opendir( $folder ) ) {
while( false !== ( $file = readdir( $handle ) ) ) {
if( $file != "." && $file != ".." && $file != "index.html" &&
!is_dir( $file ) ) {
$rand_image[] = $file;
}
}
closedir( $handle );
}
}
return $rand_image;
}
function MakeSuperRandom()
{
return srand( ( double ) microtime( time() ) * 100000 );
}
function PickRandomImages( $array )
{
$num1 = count( $array );
$num1 = $num1 - 1;
MakeSuperRandom();
$img_num = rand( 3, $num1 );
$image[] = $array[$img_num];
$num2 = count( $array );
$num2 = $num2 - 1;
MakeSuperRandom();
$img_num = rand( 3, $num2 );
$image[] = $array[$img_num];
$num3 = count( $array );
$num3 = $num3 - 1;
MakeSuperRandom();
$img_num = rand( 3, $num3 );
$image[] = $array[$img_num];
return $image;
}
function ChkArray( $array )
{
if( ( empty( $array ) ) || ( count( $array ) > 3 ) ) {
$data = 1;
} else {
$data = 0;
}
return $data;
}
function GeneratePrivKey( $array )
{
if( empty( $array ) ) {
$data = GenerateError( "Missing data for GeneratePrivKey function." );
} else {
for( $x = 0; $x < count( $array ); $x++ ) {
$keys[] = mhash( MHASH_SHA1, sha1( $array[$x] ) );
}
for( $y = 0; $y < count( $keys ); $y++ ) {
if( count( $keys ) == $keys[$y] ) {
$data .= $keys[$y];
} else {
$data .= $keys[$y] . ":";
}
}
}
return $data;
}
function GeneratePubKey( $data )
{
return md5( $data );
}
function EncData( $data, $key )
{
$td = mcrypt_module_open( 'rijndael-256', '', 'ofb', '' );
$iv = mcrypt_create_iv( mcrypt_enc_get_iv_size( $td ), MCRYPT_DEV_RANDOM );
$ks = mcrypt_enc_get_key_size( $td );
@mcrypt_generic_init( $td, $key, $iv );
$encrypted = mcrypt_generic( $td, $data );
echo "<br><b>Ciphered Text using Random Image Hash as Key:</b><pre> " .
$encrypted . "</pre><br>";
@mcrypt_generic_deinit( $td );
@mcrypt_generic_init( $td, $key, $iv );
$decrypted = mdecrypt_generic( $td, $encrypted );
echo "<br><b>De-Ciphered Text using Random Image Hash as Key:</b><pre>"
. $decrypted . "</pre>";
@mcrypt_generic_deinit( $td );
@mcrypt_module_close( $td );
}
// to use functions
$x = ReadFolder( "images/" );
$y = PickRandomImages( $x );
$b = GeneratePrivKey( $y );
echo "<b>Private Key data:</b><pre>" . $b . "</pre>";
$data = "<br>" . GeneratePubKey( $b );
echo "<b>Public Key data:</b><pre>"; print_r( $data ); echo "</pre>";
echo EncData( $credit_card_data, $b );
?>
With that code you will have to re-write the 'EncData()' function to
perform ONLY encryption as of right now it encrypts and decrypts for
demonstration purposes only.
And on another note why not use a different delivery method altogether
such as using java-script to encrypt the data prior to transmission,
store the private key inside the local network, use the public key and
associate it with the purchase within the database and develop a method
of authentication for the users to retrieve the data and then, and only
then use the private key to decrypt the data.
Just a thought.
> case, I wrote an algorithm that would encrypt these digits prior to
> sending, using the actual order number as a key. The accounting
> software I wrote (all in PHP) would then retrieve the latter half of
> the credit card number from the database, decrypt the first part of
> the credit card number from the email (entered by the sales team on an
> SSL-encrypted page), and the credit card number would be displayed in
> full on the screen, to print, process, or verify.
>
> The downside is that, if there are any problems with email and
> delivery, the first $n digits of the card might not be received by the
> sales department. While, to date, I'm not aware of this having been a
> problem for my client (knock on wood), it's still a possibility. For
> this reason, you need to be sure to either have the email address
> confirmed prior to processing the order, or require a valid telephone
> number, so that you can reach the customer in the event of a failure.
> To assure the customer that you are calling legitimately, you will
> still have the last digits of the credit card, as well as the
> expiration data and CVV number (also stored in the database), the
> billing address, and the date and time the order was placed.
>
> It may not work for you, but that's how I created the system for
> my client in 2004, and it's still being used today, with almost $8
> Million in online sales. [pats self on back] ;-P
>
> Now if I could just go back and renegotiate my contract for that gig....
>
- --
Jason Gerfen
"I practice my religion
while stepping on your
toes..."
~The Ditty Bops
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