Key derivation and entropy estimation for wireless signal strength

Mgr. Surendra Sharma

Master's thesis

Abstract:

The large scale deployments of wireless networked devices are expected to grow exponentially in the near future. New technologies are emerging rapidly, that aim to embed computing in the environment for various "smart" applications in homes, industries and cities. The necessity of robust security in design and implementation for these applications cannot be overemphasized. Security goals of confidentiality, integrity, privacy, authentication, etc. can be achieved through appropriate cryptographic primitives and protocols using strong keys. Dynamic key establishment and periodic key updates are critical requirements for these applications. Key establishment using randomness in a wireless channel is a promising method, given that a passive adversary is unable to learn key information due to uncorrelated channel. Extraction of a random bit-stream using wireless channel randomness is a multistage process in which quantization is the first stage. Multiple quantization strategies have been proposed in the literature for extracting random bits from channel. Analytical study, experimental implementation and comparative evaluation of four such popular quantization schemes has been undertaken. The relevant details of study, implementation and results for performance and effectiveness of these schemes are presented in this thesis. The trade off between performance in terms of length of extracted key-bits versus effectiveness in term of entropy is established. The log-normal channel fading characteristics and effect on non-correlated measurements by a sniffing adversary are also established in this thesis.

Keywords

Arduino, Bit extraction rate, Entropy estimation, Fading channel, Information Reconciliation, Key establishment, Key extraction, Log-normal distribution, Min-entropy, Privacy amplification, Quantization, Received Signal Strength Index(RSSI)

Language used: English

Date on which the thesis was submitted / produced: 14. 12. 2017

Thesis defence

• Date of defence: 1. 2. 2018
• Supervisor: prof. RNDr. Václav Matyáš, M.Sc.
• Reader: RNDr. Petr Švenda, Ph.D.

Masaryk University

Faculty of Informatics

Master programme / field:
Informatics / Information Technology Security (eng.)