Pengamanan Instant Messaging dengan Menggunakan Algoritma AES-256 dan RSA CRT

Abstract

The rise of digital communication through instant messaging applications has created an urgent need for secure systems to protect the confidentiality and integrity of messages from interception and unauthorized access. This study implements a secure instant messaging system by combining Advanced Encryption Standard (AES) 256-bit for text message encryption and RSA with Chinese Remainder Theorem (CRT) for key encryption. The dual encryption method was chosen as AES-256 provides high data security, while RSA CRT accelerates the encryption process of public and private keys, enabling secure key exchange. The system was developed on the Android platform, focusing solely on text encryption, including 7-bit to 8-bit ASCII characters and emojis. Performance testing showed an average key encryption time of 0.003076 seconds and decryption time of 0.0044 seconds. Message encryption required 0.10172 seconds for 500 characters and 3.25537 seconds for 19552 characters, while decryption was faster at 0.008 seconds and 0.265 seconds for the same message sizes. This system is effective and efficient for real-time communication involving small to medium-sized messages, offering a balance between high security and good time performance.