Data Encryption Standard Algorithm
The DES algorithm is based on Feistel ciper.
The Encryption Process Follows three stages:
Step 1
Given a 64-Bit Plaintext P, DES first applies a fixed initial permutation (IP) to P to obtain P0 = IP(P). Express Po = Lo Ro (L for left , R for right) where L0 is the first 32 bits of P0 and Ro is the last 32 bits of Po.
Step 2
Next it will follow a 16 rounds of Feistel Encryption
Li = Ri-1
Ri = Li-1 XOR f(Ri-1,Ki)
Ki referes to the 48bit key obtain from the key K and f is the Feistel Function.
It is ok that it sounds messy to you at this stage, we will look into it in the next post.
Step 3
Switch Left and RIght to obtain R16L16 then apply the inverse permutation to obtain the ciphertext c=IP-1(R16L16).
The initial and final permutation is called P-Boxes.
It is ok that you will ask me, what are you talking about!!??? Don't worry. I asked that question when I first come over it. I will explain it later. =)
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Nice
I wanted to learn about this useful algorithm that serves as a base in a number of security techniques and tools to protect information. You have briefly explained the complete idea behind it.
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