Frequency Analysis Attack on Ceaser Cipher using Quantum Support Vector Machine

Abstract

Quantum technology accelerated computing may have the capacity to provide solutions that are much better compared to their best known classical solutions. Quantum Algorithms reducing the complexity of problems like factorisation and searching of unstructured data has triggered a panic mode among cryptographers to analyse the security state of current cryptography schemes. The paper proposes applying Quantum enhanced State Vector Machine to the Frequency Analysis Attack on Ceaser Cipher, the simplest substitution cipher. The method is message length agnostic as it analyzes the frequency of characters and improves in accuracy with increasing message length. Previous attempts at applying QSVM were focused on using the entire ciphertext and required twice as many qubits as the length of plaintext. Our method uses a quantum circuit only as the kernel for the SVM method and can be implemented with only as many classifiers as the size of the alphabet being used in the ciphertext, irrespective of message size.