What is the difference between symmetric and asymmetric cryptography and give an example use case for each.

• A. Symmetric uses the same key (example AES for data at rest); Asymmetric uses public/private keys (example RSA for TLS or digital signatures).
• B. Symmetric uses public/private keys; Asymmetric uses shared secret.
• C. Symmetric is slower than Asymmetric.
• D. Symmetric cannot be used for data at rest.

Answer: (A)

The key distinction is how encryption keys are used. In symmetric cryptography, the same secret key is used to both encrypt and decrypt data. This makes it very fast and suitable for handling large amounts of data, such as bulk file or disk encryption, or securing data in transit once the secret key has been securely distributed. A common example is AES, often used to protect data at rest like on hard drives or in databases.

In asymmetric cryptography, a pair of keys is used: a public key and a private key. The public key can be shared openly and is used to encrypt data or to verify a signature, while the private key remains secret and is used to decrypt or to create a signature. This arrangement solves the key distribution problem and enables authentication and secure key exchange. A typical use case is TLS, where the server’s private key participates in the handshake to establish a secure channel, and digital signatures (often using RSA or ECC) verify identity and integrity.