Vulnerability of the Key Sharing Protocol Executing over the Noiseless Public Channels with Feedback

It has been proven that several recently published protocols for exchanging by keys over noiseless channels of the same authors as in the current paper, have real vulnerability to eavesdropping rooted in the attacker’s receiver optimization procedure. Moreover, we have proved that binary bits and real-valued numbers exchange protocols have zero secret capacity and are therefore unpromising in their applications. Protocols of exchanging by real-valued vectors and by matrices have nonzero secret capacity under the condition of hard decoding by eavesdroppers. The use of optimal soft decoding results in a compromise of such protocols. Thus, a problem is still open about an existence or non-existence for reliable key sharing protocols executed over noiseless public channels.