Score:1

DES next round key

cn flag

I don't understand which DES key is used in the next round of Feistel construction.

As you can see below, we use our original key that has been inserted in permuted choice 1, where we got 56 bits, divided into two halves, $C_{i-1}$ and $D_{i-1}$. We will apply the left shift rule on that key and therefore obtain 16 different keys.

Do I have to use the key number 1 that I will obtain as the second round's original key? In other words, will I have to take $K_1$ and apply left shifts to it and obtain another 16 keys from my previous round's $K_1$? Or will I use the already generated $K_2$ of the previous round?

 

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kelalaka avatar
in flag
It is missing important parts see https://en.wikipedia.org/wiki/Data_Encryption_Standard#Key_schedule
kelalaka avatar
in flag
I'll be happy if you wrote your answer..
joxavy avatar
cn flag
@kelalaka Hello, I've checked the site and I believe the keys that are generated at the start will keep being used in other rounds, that's why I understood from the Wikipedia article, meaning, I don't have to generate a new key each time, just use the previous 16 keys, I guess.
kelalaka avatar
in flag
Yes, the key schedule runs only one per encryption ( AES-NI may keep it more). That is for performance..
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