The use of multi-cloud provides highly scalable and reliable application for IT leaders to transforming their data center architectures to move from a reactive, inflexible organization to being a more proactive, a multi-cloud deployment is appropriate. Multi-cloud denotes the use of multiple independent clouds by a client or a service. Since the multi-cloud services will be migrating from single cloud to different cloud service providers it is challenging quest to procure Security issues in multi-cloud. Hence there is a need to ensure storage security in multi-cloud. So to provide the storage security at multi-cloud, we adopted the cryptography techniques in our proposed method. In cryptography, we are focusing on Deffie-Hellman key exchange protocol and elliptic curve for a reliable key generation. In this paper, we majorly focused on multi-cloud, need, benefits and security aspect relating to multi-cloud.