Cryptography Reference
In-Depth Information
but with less protection). It used to be customary under DOS and Windows
that this application would then have access to the entire computer. This is a
design error. The customer virtually gets his virus himself over the network.
[Donnhack] describes in detail how this is done. The attacker offers a nice
colorful page on the Web and hopes to lure bank customers visiting it, and
that's it basically.
This security hole (you can't speak of a 'flaw' anymore in this case) basically
allows a hacker everything, but the
Quicken
software used in the example
above made it even easier for them: home banking programs normally store
orders to the bank rather than handling them online. To save phone costs, the
customer may perhaps store his one-time passwords on the disk. A program
that somehow sometime sneaked in via Internet Explorer just needs to fit in
the attacker's 'additional order', or it modifies an order stored on the disk to
the attacker's liking. You can imagine that such an attack is not very hard to
program. Once they've 'collected' enough transfer orders, the attacker's cute
Web site disappears mysteriously, and with it the attacker and the money from
all these transactions.
So what is the banks' point in supplying one-time passwords in printed form
when users offer the passwords with their software de facto to the whole world?
Considering this case, we cannot but exonerate the banks from any fault. Who-
ever uses such 'open' systems has to be made responsible for damage incurred.
This security hole has virtually nothing to do with cryptology, but we cannot
deal with theory while ignoring the real world.
Many a Windows user may feel offended by a UNIX freak. The fact is the
security concepts of many household computers are simply insufficient for
critical tasks such as banking. And the number of critical areas increases as
more and more services are offered on the Internet.
Certainly UNIX systems (and others) have security flaws, too. A large number
of users are dealing with them intensively and they are aware of the risks.
There is still a long way to go until we'll see acceptable security in computer
technology, considering that there wasn't even an elementary security aware-
ness until recently. I only hope software vendors will not succeed in continuing
to downplay the threats. If they do, the consequences cannot be foretold.
6.5.3 Password Tokens
The protocols discussed so far are not always satisfying. Either Alice knows
a secret password,
S
0
, that Mallory can spy out, or she carries a password
