## Secret Sharing in a Multi-Cloud Environment
### How It Works  
At the application platform, the data owner determines \(n\) and \(t\) values (see Section 6) and using both calls up the application to be used, selects algorithm of choice based on our Evaluation in Section 6 after a successful sign in to the system and access level determined. It will be nice to base the choice of algorithm on performance as it relates to security, overhead cost and data size. Figure 2 shows a _3-out-of-5_ access structure, while Section 6 use _4-out-of-10_ and _2-out-of-5_. The encoded data is sent to the local main multi-cloud proxy server with router for onward dissemination to the CSPs. The proxy splits the encoded data according to a secret-sharing scheme determined access structure, and distributes each share over the Internet to different CSPs. The retrieval process is similar to the storage process as the metadata server helps to keep track of the siblings of the shares. The proxy retrieves enough corresponding shares from the cloud service providers. This retrieval involves authentication to the cloud providers. The retrieved shares are sent back to the application platform software, which decodes them and verifies their authenticity before reconstructing the data. The design incorporates unique feature in a multi-cloud environment as it uses secret sharing scheme to implement near keyless encryption using SeDaS. This is done by breaking the secret into chunks called (_k-out-of-n_) threshold in such a manner that less than \(k\) shares cannot recover the secret, thus using it for data distribution in object storage system. This is also used to implement self-destruct with equal divided shares. The incorporation of a Self-Destructive system solves the problem of cloud user's privacy as there is no way the user's data can be accessed, copied, cached or used without the data owner's consent within a pre-determined time-frame as all data and their copies become destructed or unreadable after a user-specified time, without any user intervention [3]. The self-destructive system defines two modules: a self-destruct method object; and survival time parameter for each secret key part. In this case, a secret sharing algorithm is used to implement share distribution in object storage system so as to ensure safe destruct with equally divided shares. Based on active storage framework, object-based storage interface will be used to store and manage the equal divided shares. The use and implementation of a threshold system in cloud services are a deliberate act towards implementing failover protection in the model. In normal circumstances all the service providers are used in share storage as well as secret reconstruction, but in an extreme and desperate situation, _2-out-of-5_ can be made redundant. That is to say if _2-out-of-5_ CSPs fails, data/secret storage and data reconstruction are still possible. There is also an incorporation of a Break-Glass data recovery system, implemented using one of the Proxy Servers. Just as in Secret Sharing, a trusted dealer can decide to give more shares to a more trusted and reliable participant, which will enable the secret to be reconstructed by fewer participants. SECRET leverages on this concept to implement Break-Glass data recovery by establishing an access to Multi-Cloud proxy Server II, which entails an access to CSPs 1, 3 and 5 and this in turn ensures a quick recovery of shares in order to reconstruct the secret as it is a quick link to all other CSPs and moreover, following the access structure, such access ensures the possibility of reconstructing the secret in an emergency situation. This is an important feature as there could be a period of cloud outage as stated in [23], and in such situation, data recovery could be done from 3-_out-of-5_ Cloud service providers being used for data storage. That is to say, if _2-out-of-the-5_ cloud service providers fail, data recovery is still possible in such an extreme condition.