An information system is protected from unauthorized access, modification and destruction by the help of information security. There are three prime concepts for information security which are integrity, confidentiality and availability. Integrity deals with the assurance of that the provided information is trustworthy as well as accurate. Confidentiality refers to the restriction of access or privacy of data though it is not same as privacy. Availability ensures the access of infromation by authorized user depending upon their needs. Cryptography is the process of transmitting information by using other forms of original information for secure communication in the presence of adversaries. Private Key cryptography applies the same key for encryption and decryption. Encrypted text and private key both are shared between sender and receiver. The keys used in receiver's and sender's ends may be identical or easy to be derived from one to another. Authentication is the process to validate and ensure the identity of the user. Different user authentication processes are implemented in the last two decades. CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) and OTP (One Time Password) are widely used for user authentication. CAPTCHA is a visual test on the basis of challenge and response to determine whether the user is an object or human. OTP authenticates the user for a single session or transaction. Generally, the server automatically generates the OTP which is a numeric or alphanumeric string of characters.