In some ways, the potency and effectiveness of the knowledge systems rely upon its design and the way the knowledge area unit is transmitted among totally different parties. Similarly, a crucial side of computer code development is the security of the knowledge that flows through open communication channels. One of the foremost widespread designs is User/server design which creates the centralization of knowledge storage and process modification, and supply flexibility for applying authentication strategies and coding algorithms inside info systems. whereas the number of users increases, it needs to increase the authentication and coding levels as high as possible. users/servers could be a technology that enables the opening of an associate degree interactive session between the user's browser and also the server. during this study, we tend to use users/server design to accomplish secure messaging/chat between users while not the server having the ability to decode the message. During this manner, a Server Cryptography- based mostly Secure electronic messaging System mistreatment RSA (Rivest- Shamir Adelman), it is a widely used public-key cryptography and authentication system for encryption of digital electronic messaging transactions like email over the computer network, extranet, and net, to write in code and decipher messages is developed using Java Web Application.