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DES cryptograpy question ?
Hi guys,
I have a couple of questions about DES and harsh functions.
The questions are :
Is it possible to use a harsh function to construct a block cipher with a structure similar to DES?
Because a harsh function is a one-way function and the block cipher must be reversible , how is it possible to ?
Well , the first thing we need to do is to define a harsh function.A hash function is a transformation that takes a variable-size input m and returns a fixed-size string.
Now, DES uses Feistel ciphers.In a Feistel cipher, the text being encrypted is split into two halves. The round function f is applied to one half using a subkey and the output of f is exclusive-ored with the other half. The two halves are then swapped. Each round follows the same pattern except for the last round where there is no swap.
The main thing is that DES cipher is reversible where harsh functions aren't.So , answer to the first question is NO.
As for the second one ... i just don't know .
Is there anyone who can explain it too me ?
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