Simple Filter

This is a discussion on Simple Filter within the C Programming forums, part of the General Programming Boards category; I was wondering if there was a way to make a simple filter (other than ROT13) for passwords so that ...

  1. #1
    Registered User 00Sven's Avatar
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    Simple Filter

    I was wondering if there was a way to make a simple filter (other than ROT13) for passwords so that I can put it through the filter and then save it into a text file so that it is there but not directly. I would need to make one function to filter and then another to un-filter. I just don't know where to start.
    ~Sven

  2. #2
    Slave MadCow257's Avatar
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    Table based comes to mind
    That would be where you have a static table known only to the encoder and decoder which modifies the stream. Another idea is XOR (there's a faq)

  3. #3
    Registered User 00Sven's Avatar
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    So I just make a section with a bunch of statements like...
    Code:
    if(toupper(c)=='A'){
         c='R';
    }
    and then in the decoder have it be...
    Code:
    if(toupper(c)=='R'){
         c='a'
    }
    ?????

  4. #4
    Slave MadCow257's Avatar
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    Here's an example

    Code:
    #include <stdio.h>
    
    int main()
    {
    	char table [] = "randomletters";
    	char input [] = "testinputchar";
    	char output [13];
    	unsigned int i;
    	for (i = 0; i < sizeof(input); i++)
    		output[i] = input[i] + table[i];
    	printf (output);
    }
    My code is simplified in 2 aspects. One, you would not statically allocate your output like I did, and the input and table will not be the same length. The solution is pretty easy to implement, just have an iterator that bounces back to the begining of the table once you reach the end.

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