## 3 Cloud Computing Security
### User-Centric Cloud Accountability  
Cloud accountability provides mechanisms and tools that help achieve responsibility and trust from cloud providers to users. Unauthorised data access is a primary factor in checking whether CSPs observe the legal agreement of providing accountability or if collected data are processed correctly. Users should have the user-centric ability to inform CSPs of possible harmful behaviours and errors. For instance, the right to obtain access contributes to both parties' accountability, also building an asymmetric power relationship between users and CSPs. Definitions 2 and 3 provides the logical definition and the requirement of CSP for cloud accountability [40]. **Definition 2**. : _Cloud Service Accountability (CSA): A cloud service is said to be accountable if \(\text{CSA}=\{\text{CP},\text{sc},\text{Cl}_{id},i\}\), where service contract \(\text{sc}=\{\text{sov},\text{R},\text{sla},\text{T},\text{P}\}\), \(\text{sov}=\{\text{F}_{p},\text{O}_{p},\text{F}_{c},\text{O}_{c}\}\) as the statement of work, \(\text{sla}=\{\text{F}_{p},\text{O}_{p}\}\) as the service level agreement, \(\text{P}\) represents the parties involved \(\text{P}=\{\text{s}_{p},\text{s}_{c}\}\). R is the set of rules and \(\text{T}=\{\text{start}-\text{time},\text{end}-\text{time}\}\). F\({}_{p}\) represents a set of provider's prohibited clauses, \(\text{O}_{p}\) is the provider's obligations set, \(\text{F}_{c}\) is set of consumer forbidden clauses and \(\text{O}_{c}\) consumer obligations set._  
**Definition 3**. : _General Checking of Accountability Breach: If we denote \(\text{s}\) to be a service and its corresponding invariant to be \(V=\text{v}_{1},\text{v}_{2},\text{v}_{3}\cdots\text{v}_{k}\). let the critical to accountability preconditions of \(\text{s}\) be \(\text{PR}=\{\text{pr}_{1},\text{pr}_{2},\cdots,\text{pr}_{j}\}\) and the post-conditions be \(\text{PO}=\{\text{po}_{1},\text{po}_{2},\ldots,\text{po}_{k}\}\)._  
_GIVEN: Service providers and users fulfil all sets of \(n\) preconditions, \(\forall\text{pr}\in\text{PR},\text{pr}=\text{true}\);_  
_CHECK: Making sure that there is no invalidation to any of the invariants and post-conditions, \(\forall\text{po}\in\text{PO},\text{ASSERT}(\text{po}=\text{true})\);_  
\(\forall\text{v}\in V\)_,_ _ASSERT_\((\text{v}=\text{true})\);_  
_At any instance, the CHECK fails,_  
_then there has been a breach in trust and accountability_  
[PERSON] et al. proposed the TrustCloud framework that implements abstraction layers independent of one another. The TrustCloud framework was more of a detective approach than a preventive approach, arguing that detective methodologies can supplement preventive methods because they are non-invasive, investigating external risk and risks that can arise from CSPs. [PERSON] et al. [48] proposed a mechanism for trust in the cloud using a multi-tenancy trusted computing environment model (MTCEM). The model was designed to help with the duty separation in security between the CSPs and customers. The developed model was for the IaaS service infrastructure model, whose responsibility was to separate the security responsibility of cloud infrastructures. The model was made of Platform Configuration