Graduation Year


Document Type




Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Computer Science and Engineering

Major Professor

Yao Liu, Ph.D.

Committee Member

Jay Ligatti, Ph.D.

Committee Member

Nasir Ghani, Ph.D.

Committee Member

Xinming Ou, Ph.D.

Committee Member

Kaiqi Xiong, Ph.D.


Correlation, Security, Spread Spectrum, Wireless Networks


Nowadays, wireless networking is ubiquitous. In wireless communication systems, multiple nodes exchange data during the transmission time. Due to the natural use of the communication channel, it is crucial to protect the physical layer to make wireless channels between nodes more reliable. Jamming attacks consider one of the most significant threats on wireless communication. Spread spectrum techniques have been widely used to mitigate the effects of the jammer. Traditional anti-jamming approaches like Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS) require a sender and a receiver to share a secret key prior to their communication. If this key is compromised by the jammer, the jammer can then generate the frequency hopping patterns or the spreading codes used by the communicators to disrupt the wireless communication. This dissertation includes two works as a countermeasure of jamming attacks using DSSS without the requirement of sharing a secret key.

In the first work, we propose the Randomized Positioning DSSS (RP-DSSS) scheme as an extension to RD-DSSS. RP-DSSS randomly relocates the index codes for each message. This randomization hides the indices from the adversaries and thus achieves the enhanced security. Also in this dissertation, we design an “onion” spreading technique, which encodes the random positions recursively using RP-DSSS, and pads additional spreading codes to reduce the probability that a jammer can infer these random positions.

In the second work, we propose Random Allocation Seed DSSS (RAS-DSSS) which mainly focuses on concealing a random seed from the attacker by inserting it at a random position of a spreading message. In RAS-DSSS, We develop a new technique to identify the location of a random seed at a receiver by aligning between multiple received messages. Thus, a receiver can obtain the position of a random seed, and then he can recover both a random seed then regenerating the spreading codes used to spread an original message.