International Journal of Electrical and Computer Engineering (IJECE) Vol. 11, No. 2, April 2021, pp. 1771~1779 ISSN: 2088-8708, DOI: 10.11591/ijece.v11i2.pp1771-1779  1771 Journal homepage: http://ijece.iaescore.com Enhancing cloud computing security by paillier homomorphic encryption Muna Mohammed Saeed Altaee, Mafaz Alanezi Department of Computer Science, College of Computer Science and Mathematics, University of Mosul, Iraq Article Info ABSTRACT Article history: Received Feb 8, 2020 Revised Jul 26, 2020 Accepted Nov 5, 2020 In recent years, the trend has increased for the use of cloud computing, which provides broad capabilities with the sharing of resources, and thus it is possible to store and process data in the cloud remotely, but this (cloud) is untrusted because some parties can connect to the network such as the internet and read or change data because it is not protected, therefore, protecting data security and privacy is one of the challenges that must be addressed when using cloud computing. Encryption is interested in the field of security, confidentiality and integrity of information that sent by a secure connection between individuals or institutions regardless of the method used to prepare this connection. But using the traditional encryption methods to encrypt the data before sending it will force the data provider to send his private key to the server to decrypt the data to perform computations on it. In this paper we present a proposal to secure banking data transmission through the cloud by using partially homomorphic encryption algorithms such as (paillier, RSA algorithm) that allow performing mathematical operations on encrypted data without needing to decryption. A proxy server will also use for performing re-encryption process to enhance security. Keywords: Banking data Cloud computing Homomorphic encryption Paillier algorithm RSA This is an open access article under the CC BY-SA license. Corresponding Author: Mafaz Mohsin Khalil Alanezi Department of Computer Science College of Computer Science and Mathematics University of Mosul, Main Almajmuea Althaqafia Street, Mosul, 41002-Iraq. Email: mafazmhalanezi@uomosul.edu.iq 1. INTRODUCTION Cloud computing (CC) definition that provided by National Institute of Standards and Technology (NIST) of U.S. [1]: “Cloud computing is a model for enabling convenient, on demand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) that can be rapidly provisioned and released with minimal management effort or service provider interaction. This cloud model promotes availability and is composed of five essential characteristics, three service models, and four deployment models”. The use of CC has increased rapidly in many organizations and institutions in addition to increasing issues related to CC environment at the same time, one of these issues are security challenges, which include maintaining the security of information and the securely outsourcing computation that performed by untrusted third-party (cloud). Because there is a risk that personal information as well as sensitive information may exposed by some individuals who may use them for certain purposes may be malicious [2, 3]. Utilizing CC for the banking system may help save time and costs, but also concerns about security challenges may expose customer data to disclosure. It has become possible to communicate and share data between the bank and the customer remotely without the need for high costs, but CC remains untrusted because some parties can connect to the network and expose the data so we face