What is the term for a key that is shared publicly and used to encrypt data?

• A. Private Key
• B. Public Key
• C. One-Way Function
• D. Substitution Cipher

Answer: (B)

In public-key cryptography, there is a pair of keys: a public key and a private key. The public key is shared openly so anyone can use it to encrypt messages intended for the key’s owner. The owner keeps the private key secret and uses it to decrypt those messages. This separation lets you send confidential data without having to securely share a secret key beforehand.

The other options don’t fit because the private key is not shared publicly, a one-way function describes a type of cryptographic operation rather than a shared encryption key, and a substitution cipher is an old, symmetric method that doesn’t rely on a publicly shared key pair.