Which term describes the encryption key designed to be shared publicly to allow others to encrypt messages to a recipient?

• A. Private Key
• B. Symmetric Key
• C. Hash Key
• D. Public Key

Answer: (D)

Public-key cryptography uses a pair of keys: a public key that can be shared openly and a private key that stays secret. The public key is what others use to encrypt messages destined for you, since it can be distributed widely without compromising security. Only the private key, which you keep safely, can decrypt those messages. This setup is exactly what the scenario describes: a key designed to be shared publicly so others can encrypt data for the recipient. The private key is the secret counterpart used to decrypt and to sign, which is why it isn’t meant to be shared. A symmetric key, by contrast, is a single secret key used for both encryption and decryption, requiring a secure initial exchange and isn’t meant to be public. Hashing is a different concept altogether and doesn’t provide a public-facing encryption channel for delivering messages.