(ISC)2 Certified in Cybersecurity Practice Exam

At what layer of the OSI model does data translation and encryption/decryption take place?

1. A) Layer 1 (Physical)

2. B) Layer 2 (Data Link)

3. C) Layer 6 (Presentation)

4. D) Layer 7 (Application)

The correct answer is: C) Layer 6 (Presentation)

Data translation and encryption/decryption primarily occur at the Presentation layer of the OSI model. This layer is responsible for the format and syntax of the data being communicated between applications, ensuring that data sent from the Application layer of one system can be understood by the Application layer of another. It is here that transformations such as encoding, compression, and encryption/decryption happen, making it crucial for preparing data for user applications in a compatible format. For example, if one application uses ASCII encoding while another uses EBCDIC, the Presentation layer will convert the data so that it can be properly interpreted by the receiving application. Similarly, when data is encrypted for secure transmission, the Presentation layer handles this process, ensuring that only authorized users can decrypt and understand the information. Other layers of the OSI model have specific roles; the Physical layer deals with the transmission and reception of raw bit streams over a physical medium, while the Data Link layer focuses on node-to-node data transfer and error detection. The Application layer is involved with the actual end-user application services and network services, but it does not perform data translation or encryption in the way that the Presentation layer does.