DES(Data Encrypted Standard)

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 What is DES?

  • DES is a data encrypted standard in which data is encrypted by using a formula and repeated it 16 times.
  • DES uses diffusion
  • Diffusion is defined as repetition of the formula 16 times for encryption the data/message.
  • DES perform 16 rounds.
  • Input is 64 bit plain text.
  • Output is 64 bit cipher text. 
  • Example of DES is Transposition Technique.


Step 1: Initial permutation 

Step 2: Diffusion

Step 3: Final permutation

Initial Permutation:

  • Take a Data/message of 64 bits in this step.
Diffusion:

  • performs 16 rounds 
  • In each round, a key Ki is used that is generated by round key generator.
  • Working of round 1 is as follow:


Final Permutation:
  • After performing 16 rounds, output is 64 bit cipher text/data/message.

Types of DES:
  • Double DES
  • Triple DES
Double DES:
  • Only two keys (k1 & k2) are used, and we can say that encryption is performed two times for converting the plain text into cipher text.
  • Security is less as compared to Triple DES.
  • Two times encryption for cipher text as well as two times decryption is performed for get plain text.
Triple DES:
  • It can also use two keys(k1 &k2) and also can use three keys(k1,k2 & k3).
  • More secure than double DES
  • Two times encryption or three time encryption.
  • Two time decryption or three time decryption.



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