Dissecting Credit and Calling Cards

by Krackmaster

7/27/91

DISCLAIMER:

I wrote this file not to encourage carding, frauding, or any other illegal activities. This file isill uncover secrets the world of credit/calling cards to help you understand it not to abuse it. Ti is for informational purposes only!

Credit cards are used everyday by millions of people all over the world but very few people even kn anything about it. This file will try to explain to you the various types of cards and its structr.

First of all, there are different types of cards, but I will break them down into 2 categories. Thfirst are credit cards. These are cards such as Visa, American Express, Diners, etc. The others aecalling cards. Within this category are CIID, BOC, and Corporate cards.

Credit Cards

One of the most common credit cards are the Visa cards. It will always start with a 4 and will be ther 13 or 16 digits. These are the formats: 4xxx xxx xxx xxxx or 4xxx xxxx xxxx xxxx. The last dgt is the checksum digit. The expiration dates are usually no more than 2 years in the future. Ifyo look on your card, you will see a cv or pv next to the date. The cv means that this is a commoncar but the pv means you are a preferred customer. Also, there will be the first 4 digits of your ard umber somewhere on the card. They have to match. This is the issuing bank's number. Each bank has their own uniqu4 digit number. The most common is Citibank, which is 4820 or 4128.

Another common credit card is the MasterCard. This will always begin with a 5 and will be 16 digit The format is 5xxx xxxx xxxx xxxx. Again the last digit is the checksum digit. The issuing banksid number will also appear on the card as well as being the first 4 digits of your card number.

An "entertainment card" called American Express is also common. These cards begin with a 37 and thformat is like this: 37xx xx xxxx xxxxx (15 digits). Likewise, the Discovers card is gaining in cutmers. Their format is: 6011 xxxx xxxx xxxx (16 digits). Their last digits also check for validit.

Other cards are the Diners, Carte Blanche and a Japanese card called JCB (Japanese Credit Bureau). hese are the formats:

  Diners (14 digits): 30xxx xxxx xxxxx
                      31xxx xxxx xxxxx
                      35xxx xxxx xxxxx
                      36xxx xxxx xxxxx
  Carte Blanche:      38xxx xxxx xxxxx
  JCB (16 digits):    35xx xxxx xxxx xxxx

Checksum Digit

The checksum digit is the last digit of the card number. This number is check a couple of times byhe telephone computers. If the last digit is incorrect, the card is automatically unacceptable. Tee are programs out there can validate a card for you as well as make valid looking cards for you. Bu in case you haven't figured it out or had the time to look at the code, here is how they do it.

For all types of credit cards and most entertainment cards this procedure will work. There is a subutine written in Pascal that will validate cards for you. In case you don't want to type in the coeand just want to figure it out, this is how it works:

For Visa, Mastercard, American Express, Diners (and Carte Blanche), Discovers, and JCB this mod-10 teger procedure will work.

Weight #1: 1212121212121212 (for Visa, Amex, and Diners)

Weight #2: 2121212121212121 (for Mastercard, Discovers, and JCB)

Example One: 4444 0041 3001 128? Visa card x1212 1212 1212 121 Weight #1 -------------------- 4848 0042 3002 148 result of multiplication 4+8+4+8+0+0+4+2+3+0+0+2+1+4+8 = 48 add together 4+8 = 12 add the digits of the result together 12x10 = 120 multiply by 10 120-48 = 72 subtract from first result 72 mod 10 = 2 result modular 10 equals the checksum digit or the last digit of the result Example Two: 5555 0125 1500 058? MasterCard x2121 2121 2121 212 weight #2 ------------------- 1515 0145 2500 057 result of muliplication (in this case the multiplication may have confused you. Look at the 15th digit, 8 x 2 should be 16 but if you add 1+6 that's how you get 7. 1+5+1+5+0+1+4+5+2+5+0+0+0+5+7 = 41 result of addition 4+1 = 5 add the digits together 5x10 = 50 multiply by 10 50-41 = 9 subtract first result 9 mod 10 = 9 result mod 10 equals the checksum digit

Remember to use the correct weight for the specific card. Wasn't that easy??? By the way, there ia file out there on how to make a valid American Express card by Saturday Knight (thanks S.K.!). I ade valid cards most of the time but it didn't include this procedure so some I made didn't validae nd I didn't know why. So if you want to make a valid AMEX card, be sure to use the above method. Thre are 5 other methods on making valid AMEX cards by using a cancellation bulletin.

Here's what to do (again for informational purposes only!)...

Example:

37xx xx xxxx x111x

The 37 will always be there for AMEX cards and the 111 will be the foat to look for. Everything else will be the same.

Ok, now the real stuff:

37xx xx xxxx x101x (Saturday Knight's method) || +1-2 Add 1 to the 14th digit and subtract 2 from the 15th digit. If it's 0 it means 10. Everything else will be the same. 37xx xx xxxx xx000 Add 1 to the 14th digit and subtract || 2 from the 15th digit. +1-2 37xx xx xxxx x100x Add 1 to the 12th digit and subtract | | 2 from the 15th digit. +1 -2 37xx xx xxxx x102x Convert the 102 to 201. ||| 201 37xx xx xxxx x101x Subtract 1 from the 14th digit and add || 2 to the 15th digit. -1+2 37xx xx xxxx x100x Add 2 to the 9th digit, add 4 to the | | | 11th digit and add 4 to the 15th +2 +4 +4 digit. Be sure to check the last digit with the checksum routine I just gave you. If it doesn't come out,se another card number. I've made about 99% valid cards with the above methods!

The other major credit cards cannot be made in this way, unfortunately. If there is a way, I wouldike to see a file on it!

Calling Cards

Most calling cards are issued by BOCs (Bell Operating Companies). They are always 14 digits. The rmat is their phone number and a 4 digit pin number: NPA NXX XXXX ####. The pin digits are random adthe last digit isn't a checksum digit. These cards can be used on most systems since it isn't proritary like the CIID cards.

CIID cards are AT&T only cards. They can only be processed by AT&T. The format is the same excepthat it is only validated on an AT&T-type company. This means that if you were to call MCI or Sprin nd make a call, they couldn't approve it because the database for this card cannot be accessed by he.

The other type of calling cards are corporate. These cards can be used on most systems. Again the rmat is 14 digits and the last 4 is the pin. This time the first 6 digits don't follow the NPA NXXfrmat like the BOC cards do. Here is an example: 222 059 xxxx xxxx.

Validation companies validate calling/credit cards by calling up the respective issuing company sucas Visa, AMEX, PacBell, Nynex, etc in real time. This means that it isn't a week old database. Ifacard turns out to be bogus, the BOC can update their database in a matter of seconds and the validtin company will receive a code saying to decline it because it is bad.

The database is also positive in that it will store only good cards. A negative database will holdnly cards that should not be accepted and these databases are usually found in hotels for their PMS(roperty Management System) or bong boxes (automated operators that will process operated assisted als for guests). Since the hotel's system can hold only so much, they do a download of a negative ataase from validation companies around once a week to a couple of days.

Validation companies contain information about the calls itself and can hold enough information to st you. The phone companies will usually send (depending on the service they have) the calling ani he called number, the date, time, and the calling/credit card with expiration date. The phone coman can later pull a report to see what phone numbers were trying to make calls using bogus calling/redt cards.

The major validation companies are US West Service Link, Card*Tel, and Lidb (only validates callingards).

Luhn Check Digit Routine

This routine written in Pascal will check the last digit of Visa and Mastercards to make sure it's lid.

	WEIGHT$=2121212121212121
	WLEN$=LEN(WEIGHT$)
	CLEN=LEN(CC)       (* CC = CREDIT CARD NUMBER)
	CK.DIGIT=CC[1]
	CNBR=CC[1,CLEN-1]
	CNBR.LEN=CLEN-1
	RESULT=0
	WI=CNBR.LEN
	WI=WLEN$
	FOR IX=CNBR.LEN TO 1 STEP -1
	   PRODUCT=CNBR[X,1] * WEIGHT$[WI,1]
	   FOR IDX2=1 TO LEN(PRODUCT)
		 RESULT+=PRODUCT[IDX2,1]
	   NEXT IDX2
	   WI-=1
	NEXT IX
	MULTIPLE.OF.TEN=(INT(RESULT/10)+(MOD(RESULT,10) GT 0) * 10
	TEMP.CHECK.DIGIT=MULTIPLE.OF.TEN-RESULT
	CC=(TEMP.CHECK.DIGIT EQ CK.DIGIT)
	RETURN