The present diploma paper discusses the field of authentication and cryptology as a tool for authentication. The mostly used classic ways of authentication are presented, which are often also the most vulnerable ones. The mostly used way of authentication is the one with a username and a password. As people are required to create new passwords for different webpages, they are soon sated with the big amount of them, while the passwords get bad and vulnerable, because of the great number people have to remember. To solve this problem, a web application has been developed which enables authentication without a password, by using the Bitcoin system. The users authenticate themselves with the Bitcoin address. Thus the user does not have to remember a great number of passwords anymore, while a certain amount of anonymity at login is also possible.