Encryption-based security for public networks : technique and application

Document Type



Doctor of Philosophy (PhD)


Electrical Engineering

First Advisor's Name

Subbarao Wunnava

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Kang Yen

Third Advisor's Name

Gustavo Roig

Fourth Advisor's Name

Malcolm Heimer


Integrated services digital networks, Data transmission systems, Security measures

Date of Defense



This dissertation describes the development of a new system whereby the Public Switch Telephone Network (PSTN), which is not secure, can perform like a private network. Integrated Services Digital Network (ISDN) forms a technical platform for other communication technologies, such as frame relay and Switched Megabit Data Service (SMDS). This is an original and innovative hardware and software design which can be embedded into the ISDN Customer Premises Equipment (CPE) to privatize the public ISDN without the need to upgrade the existing switching equipment. This research incorporates original design and development of the following hardware and software modules to provide real-time encryption and decryption of images and data in the ISDN medium: 1. ISDN Communications Module with customized Caller-ID access. 2. Token Access Control module for secure log-in. 3. A Hybrid Cryptographic Module, public key for key management and authentication, and private key for privacy. This Cryptographic module, the Security Extension Module to the Terminal Adapter (SEMTA), was implemented in software, and then optimized in hardware. This work proves that medical images and legal documents can be transmitted through the PSTN without any security breach, guaranteeing the privacy, confidentiality, and authenticity of the data.



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