DES(Data Encrypted Standard)

 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.