Research On Physical Layer Key Distributin Technology Based On Noisy Private Channel

Key distribution using the short-term reciprocity and space uniqueness of wireless channelis a secure communication method designed specially for wireless communication. In existingmethods, legitimate users get identical keys from channel characteristics through three phases:advantage distilliation, inforamtion reconciliation and privacy amplification. But the presenttechniques still face with three main problems. First, to get a high identical rate of extrationresult, low quantization precision is taken, resulting in a lack of key’s variety, and easy to becracked. Second, because of the openess of information reconciliation pahse, the bits exchangedmust be independent from the key, as a result only block coding can be used for reconciliation,and efficiency is low. Third, error correction methods of information reconciliation is restrictedto block coding, thus key distribution cannot be achieved in a complex communicationsenvironment. These problems limit this technology to theoretical study and cannot be appliedpractically. So relying on the National Natural Science Foundation, we have a research on thetechnolgy of key distribition based on wireless channel characteristic, and propose this newmechanism with universality “physical-layer key distribution mechanism based on noisy privatechannel”.Physical-layer key distribution mechanism based on noisy private channel use channelcharacteristics for encryption to establish private channel for key distribution. Then under theguidence of this mechanism, an adaptive quantization method of channel characteristics andadaptive coding method for increasing key distribution efficiency are researched. The maincontents are as follows:1. We propose a physical-layer key distribution mechanism based on noisy private channel.Different from the existing mechanism extracting keys from channel characteristics andreconciliation publicly, this mechanism do encryption with channel characteristics, establishing aprivate channel equivalently for key distribution. the measure error of channel characteristics actas noise in the private channel, and can be overcomed by error correction coding of keys. Thismechanism guarantee the security of both the keys and parity information, get rid of the securityrestriction in present methods. Thus any coding method can be used for different transmissionchannel, and the key is secured without privacy amplification.2. We propose an adaptive quantization algorithm formed of an quantizer offset with thequantization noise at one side and a quantization-level optimizing method, which maximize thelength of secret bit string under the constraint of mismatch rate. Based on this, we investigate theARQ error control scheme and present a key agreement policy selection approach to harvestlonger secret bit strings. With this scheme, bit strings with length close to theoretical limit can begenerated, and the mismatch rate is lower than5%.3. The key reliable distribution scheme based on adaptive coding is proposed to achievereliable distribution in complex environment. Adaptive coding is used for coding the key tomatch the private channel better under the mechanism proposed before. Thus average keydistribution rate is araised. Simulation results indicate the improvement with this scheme.