Financial identity is *dangerous*? (was re: Fake companies, real money)
Anne & Lynn Wheeler
lynn at garlic.com
Fri Oct 29 09:55:07 EDT 2004
At 10:29 AM 10/28/2004, James A. Donald wrote:
>Is there a phone that is programmable enough to store secrets
>on and sign and decrypt stuff?
>The ideal crypto device would be programmed by burning new
>proms, thus enabling easy reprogramming, while making it
>resistant to trojans and viruses.
there are a couple different trust relationships ... the issue of the user
trusting the keyboard/terminal ... and the issue of the relying party
trusting the keyboard/terminal.
The FINREAD terminal ... misc. (EU) finread references:
supposedly is certified as an stand-alone external keypad and display that
can't (very difficult) in being hacked. the financial scenario is that the
display can be trusted to display the amount being approved .... the user
puts in his card and enters their pin/password. The pin-pad is certified as
not being subject to virus keyloggers (that you might find if a PC keyboard
was being used).
For the relying party (say an online financial institution) ... the user
putting their card into the reader ... and the card generating some unique
value ... would indicate to the relying party "something you have"
authentication. The user entering a PIN can both indicate "something you
know" authentication as well as implying that the user aggrees/approves
with the value in the display.
Note that the implied agreement/approval ... in not just dependent on the
user entering the PIN ... but also on the certification of the terminal ...
that the terminal doesn't accept the PIN until after the certified terminal
displays the correct value (i.e. there is a certified business process
The entering of the PIN can also involving transmitting some form of the
PIN to the relying party ... and/or the PIN is passed to the smartcard/chip
... and the chip is known to only operate in the appropriate manner when
the correct PIN is entered. In this later case, the relying party doesn't
actually have knowledge of the "something you know" authentication .... but
the relying party can infer it based on knowing the certified business
process operation of all of the components.
Lets say the unique value provided by the smartcard is some form of digital
signature ... and the relying party infers from the correct digitial
signature "something you have" authentication. There is still the trust
issue between the relying party and the terminal used by the user ....
which may also require that the (certified eu finread) terminal also
performs a digital signature .... in order for the relying party to be able
to trust that it really was a terminal of specific characteristics ... as
opposed to some counterfeit or lower-trusted terminal.
There is still the issue of the user trusting such a terminal. If the
terminal belongs to the user .... in the user physical home space .... then
there isn't as much of a trust issue regarding the user trusting the terminal.
The problem arises for the user if they are faced with using a terminal in
some random, unsecured location some place in the world. Even in the
situation where a relying party receives a valid transaction with a valid
digital signature from a certified, known finread terminal ... there are
still a number of MITM attacks on finread terminals that might be located
in unsecured locations (various kinds of overlays and/or intermediate boxes
capable of performing keylogging and/or modified display presentation).
The personal cellphone and/or PDA ... with user "owned" display and key
entry .... is a countermeasure to various kinds of MITM attacks on
terminals in public &/or unsecured locations
(user has no way of easily proofing that they aren't faced with some form
of compromised terminal environment).
Anne & Lynn Wheeler http://www.garlic.com/~lynn/
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