S-DES Encryption and Decryption

Wokey, here it is in pictorial form. Sorry it’s handwritten. This is the detailed version, to get the bigger flowchart refer to my notes 😉

Let’s start with a 10-bit key : 1010000010.

The goal is to encrypt an 8-bit plaintext : 0100 0001

We start by key generation, to generate the two  8-bit subkeys (K1 and K2):


Next : encryption process – first loop


Then the next loop:


We ended with 0001 0101 as ciphertext, we should be able to decrypt it back to 0100 0001.  Remember, during decryption we use K2 first then K1.



Second loop of decryption process:


Done !


8 thoughts on “S-DES Encryption and Decryption

  1. Pong2 says:

    I vaguely remember how to calculate this stuff, prolly suck at it now. lg mikir how did i pass this subject. ooo ya …. dosennya pak revi and he gave me a P -_-

  2. Sanny says:

    Waduh… ga mudeng, Miss… Hehe…

    Btw, tukeran link blog ya Miss… Saya pindahan nih… ntar blog nya miss Sandy saya link ya… =)

  3. Nancy says:

    There is some thing wrong in round 2 encryption because the final result of lift and right will be replaced you forget it right?? You forget to swap the final result of right and left before you make ip inverse

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