What system is provided by the CSP, but controlled and even hosted by the customer?

The choice of client-side KMS as the correct answer is based on the concept of key management systems (KMS) in cloud security. A client-side KMS is a system where the cryptographic keys used to encrypt and decrypt data are managed and hosted by the customer, even though the underlying infrastructure or platform may be provided by the Cloud Service Provider (CSP). This empowers the customer with the control needed to enforce data security policies while simultaneously utilizing the cloud resources offered by the CSP.

By hosting the KMS on the client side, customers can ensure that they maintain full ownership of their encryption keys, which is crucial for meeting compliance requirements and protecting sensitive data from unauthorized access. This model helps in establishing a secure environment where customers can manage access to their secured data effectively.

Other options, such as customer-side KMS, remote KMS, and internal KMS, do not accurately convey the specific customer control and hosting aspects indicated in the question. While they may involve elements of key management, they do not fully capture how a client-side KMS specifically operates by allowing the customer to host and control the encryption keys themselves.