Regular Expression for Credit Card Track Data

Question

Are there any known regular expressions out there to validate credit card track 1 and track 2 data?

EDIT:

The information on track 1 on financial cards is contained in several formats: A, which is reserved for proprietary use of the card issuer, B, which is described below, C-M, which are reserved for use by ANSI Subcommittee X3B10 and N-Z, which are available for use by individual card issuers:

Track 1, Format B:

Start sentinel — one character (generally '%')
Format code="B" — one character (alpha only)
Primary account number (PAN) — up to 19 characters. Usually, but not always, matches the credit card number printed on the front of the card.
Field Separator — one character (generally '^')
Name — two to 26 characters
Field Separator — one character (generally '^')
Expiration date — four characters in the form YYMM.
Service code — three characters
Discretionary data — may include Pin Verification Key Indicator (PVKI, 1 character), PIN Verification Value (PVV, 4 characters), Card Verification Value or Card Verification Code (CVV or CVK, 3 characters)
End sentinel — one character (generally '?')
Longitudinal redundancy check (LRC) — it is one character and a validity character calculated from other data on the track. It should be noted that most reader devices do not return this value when the card is swiped to the presentation layer, and use it only to verify the input internally to the reader.

Track 2: This format was developed by the banking industry (ABA). This track is written with a 5-bit scheme (4 data bits + 1 parity), which allows for sixteen possible characters, which are the numbers 0-9, plus the six characters : ; < = > ? . The selection of six punctuation symbols may seem odd, but in fact the sixteen codes simply map to the ASCII range 0x30 through 0x3f, which defines ten digit characters plus those six symbols. The data format is as follows:

Start sentinel — one character (generally ';')
Primary account number (PAN) — up to 19 characters. Usually, but not always, matches the credit card number printed on the front of the card.
Separator — one char (generally '=')
Expiration date — four characters in the form YYMM.
Service code — three characters
Discretionary data — as in track one
End sentinel — one character (generally '?')
Longitudinal redundancy check (LRC) — it is one character and a validity character calculated from other data on the track. It should be noted that most reader devices do not return this value when the card is swiped to the presentation layer, and use it only to verify the input internally to the reader.

I've been in cc business for a while now and I have a hard time imagining why you'd need this. Generally, since track 1,2,3 are in the issuer's domain you'll often be hard pressed to find data other then PAN, expiration date and service code on the track and name data might as well be junk, I've even come across PANs that don't pass Luhn check. This is why it seems to me that you'll have quite a bit of in-production special cases to fine tune the regex to be just sensitive enough to not discard workable production data that clashes with the iso spec. — bbozo

EricWasTaken EricWasTaken · Accepted Answer · 2013-11-19T21:06:25

Here is a REGEX that works for me to pick both Track 1 and Track 2. Use this with the regex option "Dot does NOT match newline".

^%(?<FC>.)(?<PAN>[\d]{1,19}+)\^(?<NM>.{2,26})\^(?<ED>[\d]{0,4}|\^)(?<SC>[\d]{0,3}|\^)(?<DD>.*)\?|;(?<PAN>[\d]{1,19}+)=(?<ED>[\d]{0,4}|=)(?<SC>[\d]{0,3}|=)(?<DD>.*)\?\Z

I tested with this data (my reader is reading both a Track 1 and Track 2 record, in this order, for the same card I tested with - numbers and name changed below.)

%B5581123456781323^SMITH/JOHN^16071021473810559010203?
;5581123456781323=160710212423468?

The above REGEX uses NAMED CAPTURE GROUPS (the "?" that starts out each (group)) and I see the result (with RegexBuddy) as:

Match 1:    %B5581123456781323^SMITH/JOHN^16071021473810559010203?       0      54
Group "FC": B        1       1
Group "PAN":    5581123456781323         2      16
Group "NM": SMITH/JOHN      19      10
Group "ED": 1607        30       4
Group "SC": 102     34       3
Group "DD": 1473810559010203        37      16

Match 2:    ;5581123456781323=160710212423468?      56      34
Group "FC" did not participate in the match
Group "PAN":    5581123456781323        57      16
Group "NM" did not participate in the match
Group "ED": 1607        74       4
Group "SC": 102     78       3
Group "DD": 12423468        81       8

Note the second match does NOT identify FC (format code) and NM (name) in the Track 2 (match 2) since they are not used in track 2.

If your regex engine does not support NAMED GROUPS, just kill the "?" part of each of the capturing groups. Then, use position to determine each group.

Also, my single SWIPE contains BOTH track 1 and track 2 (in that order, track 1, a crlf and then track 2). According to the Wikipedia link in the original question, cards can have up to 3 tracks and readers might read tracks 1 and 2 both (or one or the other) and rarely track 3.

For this reason, I think it's a safe bet to use a REGEX that looks for both track 1 and track 2 and if you get both, you can ignore track 2 (since track 1 has more data) or whatever you wish.

Because both tracks are present in my swipes, the REGEX engine will return 2 matches with my REGEX above (assuming no read error from the reader and a reader that supports both tracks). In my case, this does not bother me and I'll simply plan to use the "first match" and ignore the second.

If you're interested only in track 1, use this regex:

^%(?<FC>.)(?<PAN>[\d]{1,19}+)\^(?<NM>.{2,26})\^(?<ED>[\d]{0,4}|\^)(?<SC>[\d]{0,3}|\^)(?<DD>.*)\?\Z

If you're interested only in track 2, use the regex:

^;(?<PAN>[\d]{1,19}+)=(?<ED>[\d]{0,4}|=)(?<SC>[\d]{0,3}|=)(?<DD>.*)\?\Z

But I see no harm in checking for both and then using the first one you get, or perhaps comparing track 1 to track 2 as an additional error checking step perhaps.

Sorry to answer what seems to be answered!

Regular Expression for Credit Card Track Data

5 Answers