What are the components of an encryption system?

Users are not a technical component of an encryption system - they interact with it, but the system operates independently of any specific user.

A decryption tool is not a separate component - it is a function of the same encryption engine, which handles both encryption and decryption operations.

Users are not a component of the encryption system itself; replacing 'data' with 'user' omits the actual subject of the cryptographic operation.

Data is the subject of encryption, the encryption engine is the algorithm or process that transforms plaintext to ciphertext and back, and key management governs the lifecycle of cryptographic keys - generation, distribution, storage, rotation, and revocation. Without any one of these three components, the system cannot function securely or completely.

This option omits the encryption engine, which is the core processing component that actually performs the cryptographic transformation - no encryption occurs without it.