Publication Date
Spring 2014
Degree Type
Master's Project
Degree Name
Master of Science (MS)
Department
Computer Science
Abstract
Homophonic substitution ciphers employ a one-to-many key to encrypt plaintext. This is in contrast to a simple substitution cipher where a one-to-one mapping is used. The advantage of a homophonic substitution cipher is that it makes frequency analysis more difficult, due to a more even distribution of plaintext statistics. Classic transposition ciphers apply diffusion to the ciphertext by swapping the order of letters. Combined transposition-substitution ciphers can be more challenging to cryptanalyze than either cipher type separately. In this research, we propose a technique to break a combined simple substitution- column transposition cipher. We also consider the related problem of breaking a combination homophonic substitution-column transposition cipher. These attacks extend previous work on substitution ciphers. We thoroughly analyze our attacks and we apply the homophonic substitution-columnar transposition attack to the unsolved Zodiac-340 cipher.
Recommended Citation
Yi, Jeffrey, "Cryptanalysis of Homophonic Substitution-Transposition Cipher" (2014). Master's Projects. 357.
DOI: https://doi.org/10.31979/etd.c27y-va9u
https://scholarworks.sjsu.edu/etd_projects/357
