What is NOT a benefit of using API keys for authentication?

Using API keys for authentication offers several benefits, but ensuring high security when keys are shared is not one of them. API keys are typically designed to be embedded in client applications, and when shared, they can be exposed to unauthorized users. This exposure undermines the security model because anyone with access to the API key can potentially gain unauthorized access to the API's resources.

Conversely, the other benefits of API keys highlight their utility in various scenarios. For instance, API keys can be revoked easily, allowing the system to quickly disable access if a key is compromised or if the user no longer needs access. They are also straightforward to implement in requests, making them an attractive choice for developers looking for a simple authentication method. Additionally, API keys can facilitate access control and rate limiting, enabling providers to manage who accesses their APIs and how frequently.

Thus, while API keys are beneficial for these reasons, they do not guarantee high security when shared, making that the correct answer to the question.