Which statement best describes the main characteristic of asymmetric cryptography?

• A. It uses a pair of keys (public and private) for encryption and decryption.
• B. It uses a single shared secret key for all transactions.
• C. It relies on symmetric algorithms for key exchange only.
• D. It cannot be used for digital signatures.

Answer: (A)

Asymmetric cryptography relies on a pair of keys: a public key that can be shared openly and a private key that remains secret. Data encrypted with the public key can only be decrypted with the private key, and data signed with the private key can be verified with the public key, enabling both confidentiality and digital signatures. This key-pair approach is what sets asymmetric cryptography apart from symmetric systems that use a single shared secret for both encryption and decryption. While asymmetric methods can be used for secure key exchange, the defining feature is the dual-key mechanism, not a reliance on symmetric algorithms. And it is indeed capable of supporting digital signatures, which is another common use of the private key.

In short, the defining trait is the use of two keys for complementary operations—public for encryption or verification, private for decryption or signing.