[Cryptography] Public-key auth as envisaged by first-year science students

[mok-kong shen]

Am 11.08.2016 um 22:10 schrieb Michael Kjörling:
> On 11 Aug 2016 09:56 -0400, from leichter at lrw.com (Jerry Leichter):
>> The devil is, of course, in the details. You need to work the
>> numbers to see how predictable the timing on legitimate exchanges
>> is, and how quickly an attacker might be able to complete the MITM
>> exchange.
>
> One thing that strikes me about the scenario you describe (low
> powered, point-to-point radio links over short distances perhaps using
> omnidirectional antennas) is that the link budget would be appropriate
> for the initial link distance (because to begin with, we assume no
> MITM of any kind is present). Hence, two devices 100 meters apart have
> a link budget that is appropriate for communication over 100 meters
> plus change. Call these two initial devices talking to each other
> Alice and Bob.
>
> If someone injects a MITM, call it Mallory, in between Alice and Bob,
> on a wireless network, then wouldn't Alice and Bob _still be able to
> communicate directly_? Unless Mallory is doubly active (not only
> functioning as a MITM attacker to intercept and handle communication
> supposedly being passed between Alice and Bob, but also disrupting
> attempts at direct communication between Alice and Bob), Alice should
> still hear Bob's transmissions and Bob should still hear Alice's. So

[snip]

This remembers me of a network "Roja" which used red (and infrared)
light and which existed about 10 years ago in the Czech Republic.
I surmise that, if the cost issue isn't essential, then a network
employing laser could have some security advantages in certain special
situations. (A recent paper on the history of "Ronja" is J. Söderberg,
"Users in the Dark: ....." in G. Alberts, R. Oldenziel (eds.), Hacking
Europe. (Springer 2014))

M. K. Shen