New Directions In The Theory Of Identification Via Channels

We study two problems in the theory of identification via channels. The first problem concerns the identification via channels with noisy feedback. Whereas for Shannon's transmission problem the capacity of a discrete memoryless channel does not change with feedback, we know from [3] and [4] that the identification capacity is affected by feedback. We study its dependence on the feedback channel. We prove both, a direct and a converse, coding theorem. Although a gap exists between the upper and lower bounds provided by these two theorems, the results of [3] and [4], namely the result for channels without feedback and the result for channels with complete feedback, are all special cases of these two new theorems, because in these cases the bounds coincide. The second problem is the identification via wiretap channels. A secrecy identification capacity is defined for the wiretap channel in analogy to the definition of [1]. A "Dichotomy Theorem" is proved which says here that the second o..