Type of Culminating Activity

Graduate Student Project

Graduation Date


Degree Title

Master of Science in Computer Science


Computer Science

Major Advisor

Jyh-haw Yeh


The advent of digital age has resulted in more television consumers switching to Digital TV with considerable improvement in image quality and ease-of-use. Consumers are able to select and view television programs and channels of choice by using a pay-per-use model or streaming video from their computer terminals. In all these use cases, the media provider requires a means by which they can restrict the consumers from watching selected programs for a pre-approved temporal interval. The consumer needs to be prevented access to certain pay-per-use channels and programs upon expiry of this pre-approved access. This necessitates the media provider to have a way to generate and assign time-bound secure access keys which could be granted and removed easily. In conventional key assignment schemes, one has to renew the keys periodically and redistribute the keys to the users accordingly. To allow a user to access all the authorized data over some temporal window, this straightforward implementation requires him/her to keep a lot of keys which is very inefficient. In contrast to conventional schemes, a time-bound hierarchical key assignment scheme updates the keys periodically according to the class hierarchy and an entity only keeps a small amount of information for deriving all his entitled keys. Wang and Laih (WL) proposed a scheme with a concept of merging, which provides a systematic way to solve the problem. Yeh-Shyam (YS) scheme has improved on the WL scheme and has theoretically shown polynomial improvement in both memory and performance requirement. In this project, we will compare and contrast these secure key generation techniques and provide comparative analytical results.