Which of the following is a common security measure in API design?

The use of API keys is a common security measure in API design because it helps authenticate users and control access to the API. An API key is a unique identifier that is issued to a client application, allowing the server to recognize and authorize the requests originating from that specific client. This authentication process is crucial in safeguarding sensitive data and services by ensuring that only authorized applications can interact with the API.

Implementing API keys also allows for monitoring and tracking of usage, which can be beneficial for detecting potential abuse or unauthorized access. Therefore, the incorporation of API keys enhances the overall security of the API by establishing a layer of protection against unauthorized access.

Other options mentioned lack important security principles. Open access for all users undermines security by exposing the API to any potential malicious actors. The absence of data validation can lead to vulnerabilities, such as injection attacks, making the API less secure. Static data handling does not inherently provide security benefits and may lead to issues if dynamic data is expected. Thus, using API keys remains a widely recommended practice for securing API access.