User talk:87.69.235.248: Difference between revisions

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Revision as of 19:00, 12 September 2011

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)[reply]

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)[reply]

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 Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "http://localhost:6011/en.wikipedia.org/v1/":): {\displaystyle 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 Failed to parse (SVG (MathML can be enabled via browser plugin): Invalid response ("Math extension cannot connect to Restbase.") from server "http://localhost:6011/en.wikipedia.org/v1/":): {\displaystyle 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)[reply]

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

remove the PNG picture
change the text of the article

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

@@ Line 6: / Line 6: @@
 :[[:File:Feistel cipher diagram.png]] also have n+1 rounds + the text says:  <math>i =0,1,\dots,n</math>, which mean n+1 rounds. [[Special:Contributions/87.69.235.248|87.69.235.248]] ([[User talk:87.69.235.248#top|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: <math>K_0, K_1, K_2, K_3, K_4</math>. The first round takes <math>L_0,R_0</math> as input uses the key <math>K_0</math> and computes <math>L_1,R_1</math>. The next round takes <math>L_1,R_1</math> as input uses the key <math>K_1</math> and computes <math>L_2,R_2</math>. Going further, the third round takes <math>L_2,R_2</math> as input uses the key <math>K_2</math> and computes <math>L_3,R_3</math>. You should see a pattern here: each round takes input <math>L_i,R_i</math> as input uses the key <math>K_i</math> and computes <math>L_{i+1]}, R_{i+1}</math>. 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 <math>K_4</math> and the output is <math>L_5, R_5</math>. More generally if the last round function is <math>K_n</math> then the result should be <math>L_{n+1]}, R_{n+1}</math> and not <math>L_{n]}, R_{n}</math>. Thus your diagram is incorrect. [[Special:Contributions/81.62.73.125|81.62.73.125]] ([[User talk: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 to choices:
+:::my file and [[:File:Feistel cipher diagram.png]] are the same/ so you have two choices:
 :::#remove the PNG picture
 :::#change the text of the article