At which OSI layer does the encryption and decryption of a message using PKI occur?

At which OSI layer does the encryption and decryption of a message using PKI occur?

• A. Physical Layer (Layer 1).
• B. Presentation Layer (Layer 6).
• C. Application Layer (Layer 7).
• D. Network Layer (Layer 3).

Answer: (B)

PKI deals with issuing and managing cryptographic keys and certificates, which enable secure exchange. The actual process of turning plaintext into ciphertext and back—data formatting and transformation for secure presentation to the application—occurs at the presentation layer. This layer handles data representation, encoding, and security transformations so that the application layer receives data in a consistent, interoperable form. Lower layers are concerned with transport, routing, and physical transmission, while the application layer interfaces with programs rather than performing the cryptographic formatting itself. In practice, protocols like TLS sit at the boundary between transport and application, but conceptually the encryption and decryption related to PKI are associated with the presentation layer.

PKI deals with issuing and managing cryptographic keys and certificates, which enable secure exchange. The actual process of turning plaintext into ciphertext and back—data formatting and transformation for secure presentation to the application—occurs at the presentation layer. This layer handles data representation, encoding, and security transformations so that the application layer receives data in a consistent, interoperable form. Lower layers are concerned with transport, routing, and physical transmission, while the application layer interfaces with programs rather than performing the cryptographic formatting itself. In practice, protocols like TLS sit at the boundary between transport and application, but conceptually the encryption and decryption related to PKI are associated with the presentation layer.