Modifying twist algorithms for determining the key length of a Vigen\`{e}re cipher

TL;DR

This paper analyzes and enhances twist-based algorithms for estimating the key length of Vigenère ciphers, introducing the twist++ algorithm which improves accuracy across various conditions.

Contribution

The paper introduces the twist++ algorithm, improving the accuracy of key length determination in Vigenère cipher analysis over existing twist-based methods.

Findings

The domain of the twist index significantly impacts algorithm accuracy.

The twist++ algorithm outperforms the twist+ algorithm in experiments.

Experimental results demonstrate improved accuracy across multiple key and text lengths.

Abstract

In this article, we analyze and improve upon the twist-based algorithms introduced by Barr--Simoson and Park--Kim--Cho--Yum for determining the key length of a Vigen\`{e}re cipher. We provide an in-depth discussion on how the domain of the twist index affects the accuracy of these algorithms along with supporting experimental evidence. We also introduce a new twist-based algorithm, the twist$^{++}$ algorithm, and show this algorithm is more accurate than the twist$^{+}$ algorithm for a wide range of key lengths and text lengths.