We will examine how the messages can be encrypted and decrypted using the complete graph and spanning tree principles from graph theory.
Introduction
The paper explores the use of graph theory, specifically spanning trees, in cryptography to secure digital communication. Spanning trees, which connect all vertices of a graph without cycles, provide an organized and efficient structure for encoding messages. In the proposed method, each character of a message is represented as a graph vertex, edges are weighted based on an encoding table, and a minimal spanning tree is constructed to determine the path for encrypting the message. This approach allows systematic transformation of the original text into an encrypted form, which can later be decrypted using the same spanning tree structure. The technique offers structural clarity, reduced complexity, and flexible encoding, demonstrating the potential of integrating graph theory with cryptography for secure information transmission.
Conclusion
In this paper, we have studied to encrypt the original plain text into numerical values by using spanning tree concept, for this first we convert the letter in plain text into vertices and join all the vertices to form cycle graph, then by using encoding table we find the value for edges so that we get weighted graph. We add extra edges for the weighted graph to form complete weighted graph. By using Kruskal’s or prim’s algorithm we can construct minimal spanning tree then convert into matrix form. In encryption process, we use public key as matrix form (upper triangular matrix) to get cipher text. In decryption process, we use inverse of public key as matrix form to decrypt the cipher text and we get the original plain text.
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