Establishing a shared secret is best described as which cryptographic concept?

• A. Hashing
• B. Key exchange
• C. Digital signature
• D. Symmetric encryption

Answer: (B)

Establishing a shared secret is about how two parties agree on a secret key to use for encryption. This is key exchange—the process that lets both sides derive the same secret without exposing it over a potentially insecure channel. Public-key based methods like Diffie-Hellman are classic examples, where each party contributes information and they compute a common key that an eavesdropper cannot derive. Hashing, by contrast, creates a fixed-size digest of data for integrity or identification and does not produce or enable a shared secret between two parties. Digital signatures provide authentication and integrity but do not establish a common key. Symmetric encryption relies on a secret key for encryption and decryption, but the phrase “establishing a shared secret” refers to the act of agreeing on that key, not the actual encryption itself.