This article introduces a cellular automaton (CA) based method to heighten the security breach of edge computing data. Edge computing is an innovative computing paradigm that controls the processing network’s edge devices. Relocating computation nearer to the resource is the main goal of edge computing. Based on the CA’s concept, a strong secret key is introduced for text cryptography. The secret key generated in this research is a 64-character key, which performs substitutions and reverse substitutions on the plain text and cipher text by dividing the text into blocks of 64 characters. The key may be to use the same or different letters to substitute the same letters of the plain text which makes it a unique key. The strength of the key is evaluating using the substitution speed, memory utilization, possible attack, and avalanche effects.