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Section J -- Smart Cards and Magnetic Stripe Cards


J-01. What is a Smart Card?

A Smart Card is a plastic card the size of a credit card with an integrated circuit built into it. This integrated circuit may consist only of EEPROM in the case of a memory card, but may also contain ROM, RAM and a CPU.

Smart cards are defined by the ISO 7816 standards.

StandardDescription
ISO 7816-1 Physical characteristics
ISO 7816-2Dimensions and location of the contacts
ISO 7816-3Electronic signals and transmission protocols
ISO 7816-4Industry commands for interchange
ISO 7816-5Number system and registration procedure for application identifiers
ISO 7816-6Interindustry data elements

ISO standard documents are available for purchase from ISO: International Organization for Standardization.

For more information on the ISO standards, visit Didya.com.

In the U.S., smart cards are utilized in GSM mobile telephones, in DirecTV and EchoStar satellite receivers, and in the American Express Blue card.

Smart cards designed for specific applications may run proprietary operating systems. Smart cards designed with the capability to run multiple applications usually run MULTOS or Java Card.


J-02. What are some common Smart Cards?

CardEEPROM StorageFeatures
SLE44181KBWrite protect
SLE44281KBWrite protect, 2 byte security code
SLE4432256B32B write-once memory
SLE4436221b24 bit ROM, 40 bit PROM
SLE4442256B3 byte security code, 32B write-once memory
ACOS1 - 1k1KBTriple DES, Authentication, 8 byte PIN
ACOS1 - 8k8KBTriple DES, Authentication, 8 byte PIN

For more smartcards, check out the product offerings from vendors like Infineon Technologies.



J-03. What is the layout of data on magnetic stripe cards?

This FAQ answer was written largely with information supplied by wea$el:

Data is laid out on a standard magnetic car in three tracks. A card may have any of these tracks, or a combination of these tracks.

Track 1 was the first track standardized. It was developed by the International Air Transportation Association (IATA) and is still reserved for their use. It is 210bpi with room for 79 7-bit characters.

Track 1 is encoded with a 7-bit scheme (6 data bits plus one parity bit) that's based on ASCII. If your reader does not perform the ASCII conversion, all you have to do is add 0x20 to each byte to turn it into ASCII (there are no "control" characters). The seventh bit is an odd parity bit at the end of each byte.


Track 1 Fields
Start sentinel 1 byte (the % character)
Format code 1 byte alpha (The standard for financial institutions
specifies format code is "B")
Primary Account number Up to 19 characters. American Express inserts space characters in here in the same places the digits are
broken up on the face of your card.
Separator 1 byte (the ^ character)
Country code 3 bytes, if used. (The United States is 840) This
is only used if the account number begins with "59."
Surname  
Surname separator (the / character)
First name or initial  
Space (when followed by more data)
Middle name or initial  
Period (when followed by a title)
Title (when used)
Separator 1 byte (^)
Expiration date or separator 4 bytes (YYMM) or the one byte separator if a non-expiring card.
Discretionary
data
Optional data can be encoded here by the issuer.
End Sentinel 1 byte (the ? character)
Longitudinal Redundancy Check (LRC) 1 byte. The LRC is made up of parity bits for each
"row" of bytes, making the total even. That means
that the total of all the bit 1s of each byte has
to come out to an even number. Same for bit 2,
etc. The LRC's parity bit is not the sum of the
parity bits of the message, but only the parity bit
for the LRC character itself. (It's odd, just like
any other single byte's parity bit.)


Track 2 was developed by the American Bankers Association (ABA) for on-line financial transactions. It is 75bpi with room for 40 5-bit numeric characters.

Track 2 is encoded with a 5-bit scheme (4 data bits plus one parity bit.) To convert this data into ASCII, add 0x30 to each byte.


Track 2 Fields
Start sentinel 1 byte (0x0B, or a ; in ASCII)
Primary Account Number Up to 19 bytes
Separator 1 byte (0x0D, or an = in ASCII)
Country code 3 bytes, if used. (The United States is 840) This
is only used if the account number begins with "59."
Expiration date or separator 4 bytes (YYMM) or the one byte separator if a non-expiring card
Discretionary data Optional data can be encoded here by the issuer.
End Sentinel 1 byte (0x0F, or a ? in ASCII)
Longitudinal Redundancy Check (LRC) 1 byte.


Track 3 is also used for financial transactions. The difference is its read/write ability. It is 210bpi with room for 107 numeric digits. Track 3 is used to store the enciphered PIN, country code, currency units, amount authorized, subsidiary account information, and other account restrictions.

Track 3 has the same properties as track 1 (start and end sentinels and an LRC byte), except that there is no standard for the data content or format. Track 3 is not currently used by any national bank card issuer.

In those rare systems where the PIN is stored on the card, this is the track where it is stored.


For more information of this topic, read the ANSI/ISO 7811/1-5 standard. This document is available from the American Bankers Association.

Other standards documents covering related topics include:


J-04. How do I determine if I have a valid credit card number?

Credit cards use the Luhn Check Digit Algorithm. The main purpose of this algorithm is to catch data entry errors, but it does double duty here as a weak security tool.

For a card with an even number of digits, double every odd numbered digit (1st digit, 3rd digit, 5th digit, etc...) and subtract 9 if the product is greater than 9. Add up all the even digits (2nd digit, 4th digit, 6th digit, etc...) as well as the doubled-odd digits, and the result must be a multiple of 10 or it's not a valid card. If the card has an odd number of digits, perform the same addition doubling the even numbered digits instead.

This program, presented in C source code form, will perform this math for you. Feed it all but the last digit of your credit card number, and it will give you the last digit. If it gives you a last digit different from the one you have, you have an invalid credit card number.

#include        <stdio.h>

/*
 * Return last digit of a bank card (e.g. credit card)
 * Receives all the digits, but the last one as input
 * By Diomidis Spinellis <dds@doc.ic.ac.uk>
 */
int bank (u)
char *u;
        {
        register i, s = 0;
        int l, t;

        l = strlen(u);
        for(i = 0; i < l ; i++)
                {
                t = (u[l - i - 1] - '0') * (1 + ((i + 1) % 2));
                s += t < 10 ? t : t - 9;
                }
        return 10 - s % 10;
        }
	
void main (argc, argv)
	
int  argc;
char **argv;
        {
        while (--argc)
                printf ("%d\n", bank (*++argv));
        }



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