Abstract: A computer network is a group of computer systems which are connected together through various communication channels which make easy use of resource-sharing between the wide ranges of users. Security was not an important and essential issue in early days. But now as billions of ordinary citizens are using networks for banking, shopping, Air Ticket Reservation, Online Examinations, Filling their Income Tax, Business, Marketing, Stock Exchange, hospitals, government organizations, and industries and so on.Computer securityis also known as cyber securityand IT security because it protects the computer system from theft or damage to the hardware, software or the information stored in it.Securityis a techniquewhich is used tomake certain data stored in a computersystem which cannot be read or translated by any persons or individuals without any authorization because it involves data encryption and password.Computer hackingis one of the technique used for modifying or altering computer software and hardware with unauthorized access to the computer system. In short term it can be called as “hackers.”This paper provides a review and survey of some of the symmetric and asymmetric techniques used in computer networks. Feature of achieving the effectiveness, flexibility, security, and efficiency.
Keywords: AES, Blowfish, Cryptography, Decryption, Symmetric Encryption, IDEA, RC4, RSA.