Safe user authentication in a network environment

Network security is often neglected even by users. This paper deals with user authentication in a network environment and offers analysis of this topic and possibilities how to increase its security by cryptographic methods. A synthetic part provides a detailed description of the design of a simple web application to authenticate users with protection against selected attacks and also its practical implementation in the form of implementation in PHP. In order to perform later testing there is also design and creation of version without protection mechanisms described in this part. The evaluation part contains the results of testing of both applications in order to demonstrate the effectiveness of methods against attacks. One of the benefits of this work is also demonstration of the necessity of appropriate choice of password by user, considering his length and combination of characters from different character sets. Another benefit is also proving, how easy is to perform such attacks as well as how easy is to implement protection against them. Last but not least, another benefit of this work is a comparison of efficiency of two different password cracking methods.