The modification of caesar cryptosystem based on binary vertices colouring

Abstract

Recently information technology has developed rapidly like the development of computer hardware and software. By the existence of internet technology, the process of data transfer can be done by others from a separate place and outside the system environment. The ease of data access remotely (using the internet) does not mean that they are always positive or good, but they also make new problems for the information world. The biggest problems when using the internet are slow access speeds and security when transferring data. Communication via internet is very susceptible to data loss or changed that caused by system errors or actions from non responsible persons. According to Kadir (2011) errors in data transfer via internet are caused by two reasons, that are the existence of human error or improper user intervention and the existence of technical errors from its system. Many efforts have been made by internet users to solve the problem of data transfer, including encoding data that will be sent in order to no user can read the data except the person has the right to receive it. Just not encoding, there is also an authentication process or validation of the data received, this is done to ensure that the data received is correct or does not changed. In this paper, the author propose a modification of the caesar cipher where if the key used previously is a real number, then we change the key into the coloring of vertices on the graph. So the key that used in this method is a graph. The core of this research is that every character of the plaintext has affiliation with each vertex of the graph, so that if the vertex of the graph gets 4 colors for example, then the characters of the plaintext affiliated with that vertex are also added with 4. This process will be repeated until all characters in the plaintext are coded according to the color of vertex. If the number of the characters plaintext is greater than the number of vertices, then the repeat process will occur until all the characters from the plaintext have affiliation with the vertex on the key graph.