Cloud computing is a model for delivering IT services where resources are retrieved from the Internet through web-based tools. A key aspect of this model is security. Data encryption is a critical security feature offered by cloud service providers to protect customer data both "at rest" (stored on disks) and "in transit" (moving across the network). This feature allows customers to secure their sensitive information within the shared, multi-tenant cloud environment, ensuring confidentiality and integrity. The other options describe responsibilities that are abstracted away from the user or are antithetical to the cloud model.

A. On-premises hosting: This is the traditional IT model where an organization manages its own servers and infrastructure locally, which is the opposite of the cloud computing model.

B. Hardware provisioning: In a cloud model, the physical hardware provisioning is managed by the cloud provider. The customer benefits from not having to perform this task.

D. Physical server maintenance: This is a core responsibility of the cloud service provider. A primary benefit of the cloud is outsourcing physical maintenance to the provider.

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1. National Institute of Standards and Technology (NIST). (2011). The NIST Definition of Cloud Computing (Special Publication 800-145).

Section 2: This document defines the essential characteristics of cloud computing, such as on-demand self-service and resource pooling. These characteristics inherently mean that the consumer does not manage or control the underlying physical infrastructure (servers, storage, etc.), making options B and D (Hardware provisioning, Physical server maintenance) responsibilities of the provider, not features for the consumer.

2. Liu, F., et al. (2011). NIST Cloud Computing Reference Architecture (Special Publication 500-292).

Section 5.3.5, "Security": This section details the security aspects of cloud architecture. It states, "The Security component provides controls to protect data confidentiality and integrity..." Encryption is a fundamental control for achieving data confidentiality, establishing it as a core feature within cloud security offerings.

3. Cisco. (2020). What Is Cloud Computing? Official Cisco Documentation.

"Benefits of cloud computing" section: This official Cisco page explains that a key benefit is the elimination of "the expense of buying hardware and software and setting up and running on-site datacenters—the racks of servers, the round-the-clock electricity for power and cooling, the IT experts for managing the infrastructure." This directly refutes options A, B, and D as features for the user. Security features, including encryption, are consistently highlighted as part of the service.