As businesses profoundly rely on cloud services security becomes a critical concern. Various emerging technologies depend on cloud computing for its intrinsic features such as scalability, storage and cost-effectiveness. While this may be true, cloud users are wary about the confidentiality and integrity of outsourced data. Security Service Level Agreement(SSLA) provides transparency between service providers and customers to guarantee security services terms are delivered as agreed in the SSLA. Since many corporations outsource security services to cloud providers, it appears necessary to develop a user-centered SSLA enforcement mechanism to verify service provider commitment.In this dissertation, the main objective is to design and adopt user centered service level agreement security enforcement mechanisms to verify the execution of SSLA and hence detect SSLA violations. First, we tackle the problem of Proof Of Encryption (PoE) and then propose two security mechanisms to verify the encryption operation by the service provider whether both parties have the encryption keys or only the service provider maintains the key. Second, we developed a security enforcement mechanism where the service requester chooses one service provider to negotiate Partial Homomorphic Encryption (PHE) algorithm so that the service requester can only query encryption results at the service provider without disclosing the ciphertext. Another SSLA security enforcement mechanism is proposed to verify third-party network scanning. A customer can verify if SSLA is violated or not by relying on a group of tester nodes called $bots$ to do the testing. Finally, in order to engage more nodes to participate in the network scanning verification, one future direction would be to develop an incentive model to motivate nodes who launch the network scanning to maximize their profit and attract more nodes. The results show that our security approaches are able to detect a deceptive service provider with high probability while reducing the overhead on the service requester which paves the way to design effective SSLA enforcement mechanisms.