Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!decwrl!decvax!ima!johnl
From: johnl@ima.ima.isc.com (John R. Levine)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Magnetic encoding on cards.
Message-ID: <4181@ima.ima.isc.com>
Date: 19 Jul 89 03:01:36 GMT
References: <2549NU013809@NDSUVM1>
Reply-To: johnl@ima.ima.isc.com (John R. Levine)
Organization: Segue Software, Inc.
Lines: 27

In article <2549NU013809@NDSUVM1> NU013809@NDSUVM1.BITNET (Greg Wettstein) writes:
>I am interested in locating any information regarding technical aspects of
>the encoding methods used to place information on the magnetic strips commonly
>found on bank cards or credit cards. ...

Glad you asked.  The magnetic stripe format is standardized in ANSI X4.16, and
the format of the card itself is in ANSI X4.13.

According to X4.16, the stripe has three tracks.  The first two are read-only,
the last is writable.  Track 1 is recorded at 210 BPI in a six-bit ASCII subset.
The data can be up to 79 characters, and contains an account number, the full
name of the holder, the expiration date, a three digit country code, and a
parity byte.  Track 2 is 75 BPI and contains the account number, expiration
date, and country code in BCD.  Track 3 is the same format as track 1; its
contents are unspecified, at least in 1983 when the standard was written.  The
content formats are conventional but don't appear to be mandatory, so any 79
bytes of six-bit text would be possible on tracks 1 or 3.

I have seen lots of mag stripe readers that plug into PCs, typically apppearing
either as a serial terminal or as "magic fingers" that type the stripe contents
on the keyboard.  I've never seen a PC stripe recorder.  I suspect that given
the fairly well founded paranoia of the credit card industry, stripe writers
would be relatively hard to get.
-- 
John R. Levine, Segue Software, POB 349, Cambridge MA 02238, +1 617 492 3869
{ bbn | spdcc | decvax | harvard | yale }!ima!johnl, Levine@YALE.something
Massachusetts has 64 licensed drivers who are over 100 years old.  -The Globe