Despite the growing deployment of mission critical applications on computing systems, trust and security continues to hinder its full adoption and deployment on cloud computing platforms. In addition to accountability and non-repudiation on the cloud deployment, end-users want to be confident of availability and reliability of services. For any cloud platform to be secure and trusted, the individual layers of the platform must be secure as there is no 'one fits all solution' for securing all the layers. This work presents a multi-layer trust security model (MLTSM) based on unified cloud platform trust that employs a fuzzy logic combination of on-demand states of several different security mechanisms, such as identification, direct and in-direct trust, across all cloud layers. In addition, results from a MATLAB-based simulation of the model are also presented. A MLTSM can improve the secure deployment of cloud infrastructure in mission critical sectors such as electrical power system operation, as it provides empirical evidence that allows direct (on-demand) determination and verification of the trust state of any given cloud computing platform or service. Such a modelling approach is useful for comparison, classification and improving end-user confidence in selecting or consuming cloud computing resources
