The best practice to meet the client’s requirement is to encrypt data client-side before uploading to the cloud and retain control of the encryption keys. This practice is also known as client-side encryption or end-to-end encryption, and it involves encrypting the data on the client’s device using a software or hardware tool that generates and manages the encryption keys. The encrypted data is then uploaded to the cloud service, where it remains encrypted at rest. The encryption keys are never shared with the cloud service provider or any third party, and they are only used by the client to decrypt the data when needed. This way, the client can maintain full control over the encryption keys and the security of the data, even when the data is stored on a public cloud service12.
The other options are not as optimal as option D for the following reasons:
A. Use the cloud service provider’s encryption services but store keys on-premises: This option is not feasible because it contradicts the client’s requirement of maintaining full control over the encryption keys. Using the cloud service provider’s encryption services means that the client has to rely on the cloud service provider to generate and manage the encryption keys, even if the keys are stored on-premises. The cloud service provider may have access to the keys or the ability to decrypt the data, which may compromise the security and privacy of the data. Moreover, storing the keys on-premises may introduce additional challenges, such as key distribution, synchronization, backup, and recovery3.
B. Use the cloud service provider’s default encryption and key management services: This option is not desirable because it violates the client’s requirement of maintaining full control over the encryption keys. Using the cloud service provider’s default encryption and key management services means that the client has to trust the cloud service provider to encrypt and decrypt the data on the server-side, using the cloud service provider’s own encryption keys and mechanisms. The cloud service provider may have access to the keys or the ability to decrypt the data, which may compromise the security and privacy of the data. Furthermore, the cloud service provider’s default encryption and key management services may not meet the regulatory requirements or the security standards of the client4.
C. Rely on Secure Sockets Layer (SSL) encryption for data at rest: This option is not sufficient because SSL encryption is not designed for data at rest, but for data in transit. SSL encryption is a protocol that encrypts the data as it travels over the internet between the client and the server, using certificates and keys that are exchanged and verified by both parties. SSL encryption can protect the data from being intercepted or modified by unauthorized parties, but it does not protect the data from being accessed or decrypted by the cloud service provider or any third party who has access to the server. Moreover, SSL encryption does not provide the client with any control over the encryption keys or the security of the data.
References:
1: Client-side encryption - Wikipedia
2: What is Client-Side Encryption? | Definition, Benefits & Best Practices | Kaspersky
3: Cloud Encryption Key Management: What You Need to Know | Thales
4: Cloud Encryption: How It Works and How to Use It | Comparitech
: What is SSL Encryption and How Does it Work? | Norton
