Which encryption algorithm is classified as asymmetric?

Asymmetric encryption algorithms utilize a key pair for encryption and decryption—one public and one private key. This is in contrast to symmetric encryption, where a single key is used for both processes.

RSA, which is identified as the correct answer, is a widely used asymmetric encryption algorithm. In RSA, the public key can be shared openly, allowing anyone to encrypt messages that only the holder of the private key can decrypt. This characteristic is fundamental for secure communication over insecure channels, enabling applications like secure web browsing and email encryption.

In contrast, the other algorithms mentioned are symmetric encryption algorithms. DES (Data Encryption Standard) and AES (Advanced Encryption Standard) employ the same key for both encryption and decryption, making them suitable for scenarios where secure key distribution can be guaranteed. RC4, while also a symmetric stream cipher, follows the same principle by using a single key for encrypting and decrypting data.

Thus, RSA stands out as the only asymmetric option in the list, exemplifying the key principles of public key cryptography.