Encryption/Decryption Program
I am trying to build an encryption/decryption program for fun. I know it won't be strong, I know people would crack it in seconds but I don't care. This is just to get to grips with it. I have code that works with the XOR encryption method. It needs a bit of work but its operating and that was my goal. What I want to do is design a very simple algorithm to replace XOR in my code. I assume that I should write a function and replace
with my algorithm e.g.
Code:
c = algo(c, *key++);
Can someone tell me how I might write a function to say increment every letter by 5, i.e. a = (a+5), b = (b+5), etc?
I should know this but I'm blanking!
Code so far:
Code:
#include <stdio.h>
int main(int argc, char*argv[])
{
FILE *fp1, *fp2;
char* key;
int c;
key = argv[1];
if(*key != '\0')
{
fp1 = fopen(argv[2],"rb");
if(fp1 != NULL)
{
fp2 = fopen(argv[3],"wb");
if (fp2 != NULL)
{
while((c=getc(fp1))!=EOF)
{
if(!*key)key = argv[1];
c ^=*(key++);
putc(c, fp2);
}
fclose(fp2);
}
fclose(fp1);
}
}
return 0;
}