Retrospective Study on Classical Homomorphic Encryption Algorithms

The field of cryptography is experiencing a new growth as a result of various homomorphic encryption techniques. It allows the user to run calculations directly on the encrypted text. The evolution of the homomorphic encryption scheme has not happened in one night, it took years of hard work by researchers. The paper studies various classical homomorphic encryption algorithms that served as a milestone in the journey of achieving a fully homomorphic encryption cryptographic model. The chronological survey of classical homomorphic encryption model is presented. A comparative analysis is done to analyze the homomorphic properties and ciphertext expansion ratio. The study has been done to clearly explain many classical homomorphic encryptions and their algorithms, making it simple for new researchers to comprehend the development of homomorphic encryption from the very first encryption algorithm, the RSA algorithm. It may help the latest researchers in the field of cryptography, to understand homomorphic encryption in-depth and its evolution.