Comment on Data Encryption Standard (DES) weakness and strength.The Data Encryption Standard (DES) is a symmetric key block cipher which takes 64-bit plaintext and 56-bit key as an input and produces 64-bit cipher text as output. The DES function is made up of P and S-boxes. P-boxes transpose bits and S-boxes substitute bits to generate a cipher.
Strength- The strength of DES lies on two facts:
a. The use of 56-bit keys: 56-bit key is used in encryption, there are 256 possible keys. A brute force attack on such number of keys is impractical.
b. The nature of algorithm: Cryptanalyst can perform cryptanalysis by exploiting the characteristic of DES algorithm but no one has succeeded in finding out the weakness.
Weakness- Weakness has been found in the design of the cipher:
a. Two chosen input to an S-box can create the same output.
b. The purpose of initial and final permutation is not clear.