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The problem of authentication of message in two very different models of communication is a proposition that calls for some examination. The first model proposed is tried out in a setting where there are no computational assumptions and the sender of communication and the receiver of that communication are linked by an insecure channel with a low-bandwidth auxiliary channel. This in turn facilitates the communication sender to authenticate manually a short message delivered to the receiver like for example typing a short string or comparing two short strings typed. In an environment that lacks computational assessment being made the model proves that for any 0 < ? < 1 there is a log? n-round protocol to authenticate all n-bit messages also In situations where only 2 log(1=?)+O(1) bits are authenticated manually, and adversaries (though unbounded computationally) the probability exists to cheat the receiver into accepting a fraudulent message. There also exists a proof technique that shows the protocol discussed above is optimal as it provides a lower bound of 2 log(1=?) ? O(1) of the manually authenticated strings required length. Traditional message authentication model is the second communication model that is being proposed for examination. In this second model the sender of communication and the receiver of communication collectively shares a short key that is but however are connected only by an insecure channel. Finally it can be concluded that for the existence of protocols breaking the lower bounds discussed above it is necessary to have one-way functions especially in a computational setting.
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