Information-Theoretic Security Sample Clauses

Information-Theoretic Security. The perfect security in Figure 1.3 is acquired by concatenation of a one-time pad system and a channel encoder-decoder. That is, the enciphering-deciphering step is separated from the encoding-decoding step. In Example 1.1, the overall channel from input terminal of the encoder to the output terminal of the decoder is assumed to be noiseless. Hence, condition (1.9) is applied to the design of the one-time pad system in Figure 1.3. Now, suppose a noisy wiretap channel in which the encoding and enciphering can be jointly implemented in one step as well as the decoding and deciphering. The question is if condition (1.9) is still required to provide perfect security in this new model. If yes, a perfectly secure communication system would be still practically infeasible because of the key-distribution issue. If no, violation of condition (1.9) might result in an implementation of a secure communication system with no key-distribution concerns. In 1975, Xxxxx [11] proved that the security4 is achievable in an asymptotic sense (see Definition 1.8) with no pre-shared key if Xxx receives a noisy copy of Bob’s received signal 4We reserve term perfect security only for Xxxxxxx’x criterion for security given in Definition 1.6. Bob’s Decoder Main Channel Xxxxx’s Encoder W(x|M ) Source M x y Mˆ = Ð(y) Xxx’s Receiver I Wiretap Channel z (M ;z) n