[1080] in cryptography@c2.net mail archive
Re: Thoughts on the next target.
daemon@ATHENA.MIT.EDU (Colin Plumb)
Tue Jun 24 17:22:47 1997
Date: Tue, 24 Jun 97 14:31:38 MDT
From: colin@nyx.net (Colin Plumb)
To: cryptography@c2.net
I don't know if everyone is aware, but all of the ATM cards floating
aroud use DES to protect the PIN. With ine key sealed in tamper-proof.
Wouldn't *that* be a fun key to have?
The details are published somehwere. Basically, you encrypt some card
info to get a 16-character hex string. Some 4 nybbles of that, reduced
mod 10 (so 0-5 are more likely than 6-9) are the "master PIN".
An offset from this (added per-digit, mod 10) is stored in clear on the card
to allow programmable PINs. But most cards ship with the offset set
to 0 and the default PIN is the master PIN.
You just need a few people with closed accounts to volunteer their
ATM cards to mag stripe readers. The work would be somewhat greater
since you need to do multiple decryptions to get a full validation;
you'd need to do weed out the impossible in stages.
I'm not sure if the fraud possibilities (it lets you recover the
PINs from stolen ATM cards) are worth it, but it would sure raise
a ruckus...
--
-Colin
