[Cryptography] Secret key agreement by public discussion from common information

[Ben Laurie]

On 5 March 2016 at 22:43, mok-kong shen <mok-kong.shen at t-online.de> wrote:
>
> There is a paper: U. M. Maurer, Secret key agreement by public discussion
> from common information, IEEE Trans. Inf. Theory, 39(3) 733-742 of 1993,
> with an IMHO fairly impressive title but having apparently for some unknown
> reasons been hithertofore ignored in the common textbooks on modern
> cryptography. The material there is way above my humble knowledge, hence my
> request: Could some experts kindly give a sketch of the main idea of the
> paper such that one could get at least a certain rough comprehension of it?
> Are there good open-source implementations of that key agreement scheme?

The short answer, AIUI, is that you can exploit a noisy broadcast
system such that the two cooperating parties get an advantage over the
eavesdropper. In retrospect, this seems obvious (e.g., A tells B
something, B asks A to repeat certain parts B thinks were badly
received, A resends them. E gets noisy versions of the original
transmission, the request for repeats, and the repeats. It seems
inevitable E ends up knowing a little less than B).

Once you have a disparity of information, you can leverage that up into a key.

The snag is, we have worked hard to eliminate the noise from broadcast. :-)

But its a really interesting idea.