A device or piece of equipment which uses cryptographic logic to protect information by converting plain text to cipher text and vice versa.

• A. Cryptographic device
• B. Custodian
• C. Cybersecurity
• D. Courier

Answer: (A)

The main idea here is identifying something that actually performs encryption by applying cryptographic logic to transform data. A cryptographic device is precisely a device or piece of equipment that carries out encryption and decryption, converting plaintext into ciphertext and back again, often with built‑in key management and security protections. The other terms describe a person who handles assets (custodian), the overall field of protecting information (cybersecurity), or a person who transports items (courier), none of which specify a device that performs the cryptographic operations. So the device-focused term best fits the description.