Which of the following layers of the OSI model is responsible for end-to-end encryption?

The Presentation Layer (Layer 6) of the OSI model is primarily responsible for data format translation, compression, and encryption/decryption, ensuring that data transmitted between applications is in a usable format. End-to-end encryption, such as SSL/TLS often conceptually operating here or just above it, ensures that the application-level data is protected from its origin to its destination.

The Application Layer (Layer 7) provides network services to end-user applications but typically relies on lower layers for encryption, though some application-specific encryption can occur here.

The Session Layer (Layer 5) establishes, manages, and terminates connections between applications but does not handle encryption itself.

The Transport Layer (Layer 4) provides reliable data transfer and flow control but does not natively provide end-to-end encryption for the application data itself, though transport security protocols like IPsec operate at or below it for network-level security.