User talk:87.69.235.248

Your digaram of a Feistel cipher

I reverted your edit, because your diagram is wrong. Either you describe a cipher with n rounds. Then the round keys have indices from 0 to n-1. and the ciphertext blocks have indices n. In this case the text needs to be changed too. Or you describe a Feistel cipher with n+1 rounds. Then the round keys should have indices running from 0 through n and the ciphertext blocks have indices n+1. 81.62.73.125 (talk) 17:03, 12 September 2011 (UTC)

File:Feistel cipher diagram.png also have n+1 rounds + the text says: $i=0,1,\dots ,n$, which mean n+1 rounds. 87.69.235.248 (talk) 17:43, 12 September 2011 (UTC)

OK, let's try this with an example. Assume n=4. Hence there are 5 rounds, which have five round keys: $K_{0},K_{1},K_{2},K_{3},K_{4}$. The first round takes $L_{0},R_{0}$ as input uses the key $K_{0}$ and computes $L_{1},R_{1}$. The next round takes $L_{1},R_{1}$ as input uses the key $K_{1}$ and computes $L_{2},R_{2}$. Going further, the third round takes $L_{2},R_{2}$ as input uses the key $K_{2}$ and computes $L_{3},R_{3}$. You should see a pattern here: each round takes input $L_{i},R_{i}$ as input uses the key $K_{i}$ and computes $L_{i+1},R_{i+1}$. I.e. the index of the result is always by 1 larger than the input and the index of the round key. I.e. for n=5, the last round key is $K_{4}$ and the output is $L_{5},R_{5}$. More generally if the last round function is $K_{n}$ then the result should be $L_{n+1},R_{n+1}$ and not $L_{n},R_{n}$. Thus your diagram is incorrect. 81.62.73.125 (talk) 18:41, 12 September 2011 (UTC)

my file and File:Feistel cipher diagram.png are the same/ so you have two choices:

1. remove the PNG picture
2. change the text of the article

changing again to File:Feistel cipher diagram.png is stupid 19:00, 12 September 2011 (UTC)

Once again, the result in the diagram should be $L_{n+1},R_{n+1}$ and not $L_{n},R_{n}$. Make a concrete example and see for yourself. So please fix this mistake. And please abstain from calling me stupid. 81.62.73.125 (talk) 19:07, 12 September 2011 (UTC)

sorry. I didn't mean that you are stupud. I didn't understand the problem until now, so i thout your acion is stupid. my english is very bad, so I gess "stupid" was the wrong word to use. sorry again. 87.69.235.248 (talk) 19:14, 12 September 2011 (UTC)