eng Science and Education Publishing Journal of Computer Sciences and Applications 2328-725X 2020-09-23 8 2 56 61 10.12691/jcsa-8-2-3 JCSA2020823 article Michael M Kangethe mich01mk@gmail.com 1 Elisha Odira Abade 1 School of Computing and Informatics, University of Nairobi, Nairobi, Kenya The need for simple secure substitution encryption algorithms has risen due to complexities derived from current encryption algorithms, which over-complicate the process through many sub-processes and consume more space than necessary. This also creates the need for a secure string encryption approach that can also be applied using a simple pen and paper to encrypt and decrypt messages between each other. In this paper we present a technique based on a Non-Deterministic directional NxN chart-based encryption cipher as a solution to this problem. This will be achieved by using a 2-dimensional N by N chart as the key while using a dynamically selected directional approach to generate both the cipher and plain-text. http://pubs.sciepub.com/jcsa/8/2/3/jcsa-8-2-3.pdf encryption decryption ascii strings plain text cipher text multi dimension hex non-deterministic random selection text cipher key chart IV (Initialization Vector) XY (Horizontal/Row Vertical/Column)