Tamperproof, yet playing Tetris.

Anne & Lynn Wheeler lynn at garlic.com
Sat Jan 6 15:43:33 EST 2007

Perry E. Metzger wrote:
> Handheld "Chip & Pin" terminals for reading credit cards in the UK are
> required to be tamperproof to avoid the possibility of people
> suborning them. Here is a report from a group that has not merely
> tampered with such a terminal, but has (as a demo) converted it into a
> tetris game to demonstrate that they can make it do whatever they
> like.
> http://www.lightbluetouchpaper.org/2006/12/24/chip-pin-terminal-playing-tetris/

a couple mentions of the same	

Game over for Chip and PIN?
Hacked Chip and PIN terminal plays Tetris
Chip and Pin fraud alert

misc. past posts on related vulnerabilities and exploits

as an aside ... some of the "overlay" type of exploits that make the news about automatic teller machines have also been used with point-of-sale terminals ... somewhat a man-in-the-middle attack ... even if it is only being used for skimming information (as in most of the automatic teller machine scenarios) .... aka how does the consumer know they are dealing with the real-terminal ... or an MITM/middle-man terminal? various past posts mentioning MITM-attacks

the EU finread standard attempted to address some of the same issues ... providing tamper resistant personal-use terminals (addressing some of the same tamper resistant characteristics as point-of-sale terminals)

two of the issues

1) is the transaction you "see", the same as the transaction you "approve"

2) independent pin-entry ... as countermeasure to the numerous PC-based keylogging vulnerabilities 

there is somewhat reduced concern that a terminal (that you always have physical possession
of) ... being subverted with some sort of overlay technology (i.e. there isn't an actual
attack the tamper-resistant characteristics of the operating point-of-sale terminal ... 
but there is a MITM overlay). Cellphone and PDAs use at POS have also been suggested
as countermeasure to the variety of point-of-sale terminal exploits.

In X9a10 financial standards working group .... recent mention in this post
http://www.garlic.com/~lynn/aadsm26.htm#18 SSL (https, really) accelerators for Linux/Apache?

one of the things looked at for X9.59 standard

was how can the relying/authorizing party really know the integrity characteristics of the transaction environment. so x9.59 allowed for the transaction environment (point-of-sale terminal, finread terminal, etc) to also digitally (co-)sign the transaction. the authorizing party can
look-up the integrity characteristics of the terminal used in the transaction environment (and also have some assurance that terminal was actually used for the transaction based on verifying its digital signature with onfile public key).

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