Which of the following encryption algorithms is based on the Fiestal structure?

The Data Encryption Standard (DES) is a symmetric block cipher that explicitly utilizes the Feistel network structure for its encryption rounds. In contrast, AES employs a Substitution-Permutation Network rather than Feistel. Since RSA is asymmetric and RC4 is a stream cipher, neither fits the description of a Feistel-based block cipher.