Award Date


Degree Type


Degree Name

Master of Science in Computer Science


Computer Science

First Committee Member

Evangelos Yfantis

Second Committee Member

Andreas Stefik

Third Committee Member

John Minor

Fourth Committee Member

Sarah Harris

Number of Pages



With the advancement of quantum computing (QC), the integrity of cryptography has been called into question. For example, two QC algorithms have been developed that can break asymmetric encryption (i.e., Grover’s, Shor’s), which also poses a threat to symmetric encryption. Asymmetric encryption efforts addressing this threat include lattice-based cryptography, which uses lattice problems to reduce efficiency of cryptanalysis. Symmetric encryption security can be bolstered by increasing the key length, allowing for additional permutations a key could have; known as keyspace. This thesis seeks to expand the keyspace of symmetric encryption in order to create more possibilities. This fortification to the Advanced Encryption Standard (AES) would increase the complexity of encryption and make cipher texts more resistant to attacks. A key component of the AES is the application of byte-substitution using a predetermined mapping. We propose the possibility to change mapping between rounds while still being able to encrypt and decrypt messages without loss of information. The process described in this paper allows the user to choose the substitution box mapping for each round and would increase the keyspace to create 4.97 x 10^86 unique permutations compared to 3.4 x 10^38 permutations currently afforded by 128-bit AES encryption. By enacting this type of fortification, the AES becomes more robust, protecting data against QC attacks.


Advanced Encryption Standard; Cryptography; Quantum Computing; Symmetric Encryption


Computer Sciences

File Format


File Size

815 KB

Degree Grantor

University of Nevada, Las Vegas




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