Graduate Studies


Date of this Version

Spring 5-2014


Yaoxin Liang. Secret Key Generation for Symmetric Cryptosystem in Wireless Networks. MS thesis, University of Nebraska, 2014.


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Computer Science, Under the Supervision of Professor Ziguo Zhong. Lincoln, Nebraska: May, 2014

Copyright 2014 Yaoxin Liang.


Secure wireless communication requires the establishment of a secure channel, which is challenging and costly in a lot of scenarios. To provide secret keys for symmetric cryptosystems in wireless networks, previous research has studied the pairwise secret key generation based on the shared information between legitimate entities by exploiting the characteristics of the wireless channel. However, most of the variables they use are measured in the time domain, and heavily depend on the dynamic environments to get enough entropy. Fast key generation is impossible with stationary entities when the environment is relatively stable. To release this constraint, we choose the pairwise radio power spectrum as an alternative, i.e., the radio signal strength (RSS) measurements in the frequency domain, collected at two ends of a link to extract the keys. To our best knowledge, this variable is for the first time utilized in the secret key generation to get two highly correlated bit streams as ``fuzzy'' secret keys and advances the RSS measurements in the time domain in prior research.

Instead of carrying out information reconciliation on the fuzzy keys, a traditional method to handle the inevitable mismatching between keys due to non-ideal working environments before using them, the design developed in this thesis uses the fuzzy keys directly in the proposed symmetric cryptosystem by borrowing the error correcting ability of Forward Error Correction code. The design can not only be used as a light-weight cryptosystem, but also distribute keys to support other cryptosystems. It's resistive to both passive and active attacks. In fact, the design is motivated by the spatial irregularity of the radio power spectrum, a critical observation that paves the function of the proposed mechanism and is carefully verified with both empirical experiments and theoretical analysis.

Advisor: Ziguo Zhong