<abstract xmlns="http://www.w3.org/1999/xhtml"><p>Fully homomorphic encryption (FHE) has been among the most popular research topics of the last decade. While the bootstrapping-based, public key cryptosystems that follow Gentry’s original design are getting more and more efficient, their performance is still far from being practical. This leads to several attempts to construct <italic>symmetric</italic> FHE schemes that would not be as inefficient as their public key counterparts. Unfortunately, most such schemes were also based on (randomized) linear transformations, and shown to be completely insecure. One such broken scheme was the Matrix Operation for Randomization and Encryption (MORE). In a recent paper, Hariss, Noura and Samhat propose Enhanced MORE, which is supposed to improve over MORE’s weaknesses. We analyze Enhanced MORE, discuss why it does not improve over MORE, and show that it is even less secure by presenting a highly efficient ciphertext-only decryption attack. We implement the attack and confirm its correctness.</p></abstract>

Fully homomorphic encryption (FHE) has been among the most popular research topics of the last decade. While the bootstrapping-based, public key cryptosystems that follow Gentry’s original design are getting more and more efficient, their performance is still far from being practical. This leads to several attempts to construct symmetric FHE schemes that would not be as inefficient as their public key counterparts. Unfortunately, most such schemes were also based on (randomized) linear transformations, and shown to be completely insecure. One such broken scheme was the Matrix Operation for Randomization and Encryption (MORE). In a recent paper, Hariss, Noura and Samhat propose Enhanced MORE, which is supposed to improve over MORE’s weaknesses. We analyze Enhanced MORE, discuss why it does not improve over MORE, and show that it is even less secure by presenting a highly efficient ciphertext-only decryption attack. We implement the attack and confirm its correctness.

Cryptanalysis of Enhanced More

Tatra Mountains Mathematical Publications

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

{"article-title":"Cryptanalysis of Enhanced More"}

Fully homomorphic encryption (FHE) has been among the most popular research topics of the last decade. While the bootstrapping-based, public key cryptosystems...

Cryptanalysis of Enhanced More

Published Online: Aug 15, 2019

Page range: 163 - 178

Received: Aug 13, 2018

DOI: https://doi.org/10.2478/tmmp-2019-0012

Keywords
Homomorphic Encryption, Symmetric encryption, Cryptanalysis, Key-recovery

© 2019 Damian Vizár et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Cryptanalysis of Enhanced More

Published Online: Aug 15, 2019

Page range: 163 - 178

Received: Aug 13, 2018

DOI: https://doi.org/10.2478/tmmp-2019-0012

KeywordsHomomorphic Encryption, Symmetric encryption, Cryptanalysis, Key-recovery

© 2019 Damian Vizár et al., published by Sciendo

This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Keywords
Homomorphic Encryption, Symmetric encryption, Cryptanalysis, Key-recovery