DES(Data Encryption Standard) Algorithm

The DES algorithm takes the plain text of 64-bit as input & produces a ciphertext of 64-bit using a key of 56 bits. Initially, a 64-bit key length is used but an 8-bit is discarded.

The (DES) Data Encryption Standard Algorithm was developed by the IBM team in the 1970s.

The National Institute of Standards and Technology (NIST) later adopted this algorithm.

The DES encryption algorithm uses symmetric keys, which means that the same key is used for encrypting and decrypting the data.

DES Algorithm Steps

• The initial permutation (IP) function receives the 64-bit plaintext block.
• The IP is performed on plaintext.
• The IP then makes two halves of the block that has been permutated. The two halves are known as left plan text (LPT) and right text (RPT).
• All LPTs and RPTs are encrypted 16 times.
• The LPT and RPT are joined, and then the final permutation (FP) is performed on this block.
• The 64-bit ciphertext is now ready.

In the encryption process (step 4), there are five stages:

• Key transformation
• Expansion permutation
• S-Box permutation
• P-Box permutation
• XOR, and swap

In the decryption process, the same algorithm is used with the order of the 16 keys reversed.

The DES algorithm is used whenever a not-very-strong encryption is needed. It can be used in random number generators or even as a permutation generator.

One of the most important practical applications of the DES algorithm is to create triple DES legacy systems with three keys.