What is the primary purpose of symmetric key encryption?

• A. Share a secret key, this is primarily used to achieve confidentiality
• B. Public key distribution
• C. Non-repudiation
• D. Key escrow

Answer: (A)

Symmetric key encryption is built around using the same secret key to both encrypt and decrypt data. The main purpose is confidentiality: as long as the key stays secret, anyone who intercepts the ciphertext cannot read the message. It’s efficient for protecting large amounts of data, which is why it’s widely used in secure communications. The trade-off is securely sharing the secret key between parties, which is why it’s often paired with asymmetric methods for key exchange. This approach does not provide non-repudiation (that relies on digital signatures) and is not about key escrow (holding keys for later recovery).