Public-key cryptography is exemplified by which algorithm mentioned in the material?

• A. RSA
• B. DES
• C. AES
• D. Vigenère

Answer: (A)

Public-key cryptography uses a pair of keys: a public key for encryption and a private key for decryption, which makes secure key exchange and digital signatures possible without sharing a secret key ahead of time. RSA is a foundational public-key algorithm that embodies this approach and is widely cited as the example of public-key cryptography in modern material. DES and AES are symmetric algorithms that rely on the same key for both encryption and decryption, so they do not illustrate public-key cryptography. Vigenère is an historic, insecure cipher that does not use a public-private key pair. Therefore, RSA best fits the concept being illustrated.