Which of the following is NOT a common use for symmetric encryption?

• A. Banking
• B. Data Storage
• C. Digital Signatures
• D. Email encryption

Answer: (C)

Symmetric encryption is all about keeping data confidential by using the same key to both encrypt and decrypt. It’s extremely fast and well-suited for handling large amounts of data, which is why it’s commonly used in contexts like securing banking communications, protecting data at rest, and wrapping email content after a secure channel has established a session key.

Digital signatures, on the other hand, are about proving who created a message and ensuring it hasn’t been altered, which requires a mechanism for verification by others. That verification relies on a pair of keys: a private key to sign and a public key to verify. This is a hallmark of public-key (asymmetric) cryptography, not symmetric cryptography. Since everyone would need access to the signing key or to share a secret key with every verifier, symmetric encryption isn’t suitable for creating verifiable signatures. That’s why digital signatures aren’t a common use for symmetric encryption.