In order to be able to recover your decryption key, suppose that you decide to use Shamir$$s secret sharing scheme. Shamir's Secret Sharing is an approach to share secret, where a secret is divided into parts, giving each participant its own unique part. To reconstruct the original secret, a minimum number of parts is required.

Following Shamir$$s secret sharing scheme, suppose that you divide your decryption key into $4$ parts, storing $4$ parts in four different clouds as shown in Figure $2.$ If you lost your decryption key, you should be able to recover it with any $3$ parts.