How many rounds does DES have?

How many rounds does DES have?

• A. 8
• B. 12
• C. 16
• D. 20

Answer: (C)

DES uses a Feistel structure that runs through sixteen rounds. In each round, a subkey is combined with the right half, the result goes through nonlinear S-box substitutions and a permutation, and then is XORed with the left half before a swap. This sequence repeats sixteen times, producing the final encrypted output. The choice of sixteen rounds reflects a balance chosen during DES’s design to provide enough diffusion and nonlinearity to resist known cryptanalytic techniques of the era while keeping performance practical. Fewer rounds, like eight, would leave the cipher more vulnerable to attacks; intermediate counts such as twelve or twenty rounds don’t align with the standard DES specification. Thus, the standard DES procedure uses sixteen rounds.

DES uses a Feistel structure that runs through sixteen rounds. In each round, a subkey is combined with the right half, the result goes through nonlinear S-box substitutions and a permutation, and then is XORed with the left half before a swap. This sequence repeats sixteen times, producing the final encrypted output. The choice of sixteen rounds reflects a balance chosen during DES’s design to provide enough diffusion and nonlinearity to resist known cryptanalytic techniques of the era while keeping performance practical. Fewer rounds, like eight, would leave the cipher more vulnerable to attacks; intermediate counts such as twelve or twenty rounds don’t align with the standard DES specification. Thus, the standard DES procedure uses sixteen rounds.