[Cryptography] Paper check security

John Levine johnl at iecc.com
Thu Oct 1 17:08:03 EDT 2015


> But I haven't heard anything at all about the security of paper
> checks. Banks now allow such checks to be deposited by scanning them
> or even photographing them with a smart phone. This defeats more than
> a century of inventions designed to make paper checks unforgeable. ...

A lot of those inventions date from the era when printing presses were
large and heavy and only found in print shops.  The US is unusual in
that you can get your checks printed anywhere, rather than getting
them from your bank, which rules out most of the techniques unless
you're planning to licence check printers.

Back in 2004, the Check 21 act allowed banks to scan paper checks and
process the images, rather than returning the physical paper, known in
the biz as check truncation.  For recipient banks that couldn't handle
image files they printed them out in a form called a substitute check,
but I haven't seen one of those for years.  As you note, a lot of
checks are now truncated before they get to the bank, by phone apps,
bank websites (one of mine lets me upload scanned images), and point
of sale terminals which as often as not scan your check and the clerk
gives it back to you.

If the check's going to be scanned, most of the anti-forgery
techniques are pointless, since a scanner can't tell nice paper with a
hologram from something you just printed on your deskjet.

The real security in checks is that they can be repudiated, sort of
like credit card transactions.  If you see a bogus check on your
statement, you can challenge it, and there's a bunch of stuff in
the UCC about what happens then.

R's,
John

PS: In Canada you get your cheques from the bank and they have a small
hologram.  In the UK you get your cheques from the bank, but they have
no anti-forgery features I can see.  In France you get your cheques
from the bank, and they have seven digit cheque numbers which the bank
probably links with your account.  I've never used a cheque in France
because everyone who might take one prefers my credit or debit card.


More information about the cryptography mailing list