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/*
* A Four Square cipher decoder. (Don't look directly at the mess)
*
* Copyright (C) 2014 Tomasz Kramkowski <tk@the-tk.com>
*
* This program is free software. It is licensed under version 3 of the
* GNU General Public License.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see [http://www.gnu.org/licenses/].
*/
#include <stdio.h>
#include <ctype.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>
#define Q ('Q'-'A')
#define CTOI(c) ((c) - 'A')
#define ITOC(c) ((c) + 'A')
struct vec2 {
int x;
int y;
};
int increinc(int *);
void preprocess(char *);
void genkey(char *, char *);
struct vec2 *newVec2(const int, const int);
int main(int argc, char **argv)
{
int x, y, c = 0, i;
char trfullkey[26], blfullkey[26], *trkey, *blkey, *cipher;
struct vec2 trtable[25], bltable[25];
if(argc!=4){
printf("Usage: %s <key1> <key2> <cipher>", *argv);
exit(1);
}
printf("%s, %s ", *(argv+1), *(argv+2));
trkey = argv[1];
preprocess(trkey);
genkey(trkey, trfullkey);
blkey = argv[2];
preprocess(blkey);
genkey(blkey, blfullkey);
cipher = argv[3];
preprocess(cipher);
i = 0;
for(x=0; x<5; x++)
for(y=0; y<5; y++) {
trtable[CTOI(trfullkey[i])].x = x;
trtable[CTOI(trfullkey[i])].y = y;
i++;
}
i = 0;
for(x=0; x<5; x++)
for(y=0; y<5; y++) {
bltable[CTOI(blfullkey[i])].x = x;
bltable[CTOI(blfullkey[i])].y = y;
i++;
}
char basetable[5][5];
for (x = 0; x < 5; x++)
for (y = 0; y < 5; y++){
if (c == Q)
c++;
basetable[x][y] = 'A' + c++;
}
for(size_t i = 0; i < strlen(cipher) / 2; i++){
char c1 = cipher[2*i];
char c2 = cipher[2*i+1];
putchar(basetable[trtable[CTOI(c1)].x][bltable[CTOI(c2)].y]);
putchar(basetable[bltable[CTOI(c2)].x][trtable[CTOI(c1)].y]);
}
putchar('\n');
return EXIT_SUCCESS;
}
inline int increinc(int *num)
{
(*num)++;
return (*num)++;
}
void preprocess(char *str)
{
char *src = str, *dest = str;
while (*src != '\0') {
if (isalpha(*src))
*(dest++) = toupper(*src);
src++;
}
*(++dest) = '\0';
}
void genkey(char *input, char *output)
{
bool dict[26] = {0};
int ii = 0;
for (size_t i = 0; i < strlen(input); i++) {
if (!dict[CTOI(input[i])]) {
output[ii++] = input[i];
dict[CTOI(input[i])] = true;
}
}
for (unsigned i = 0; i < 26; i++)
if (!dict[i] && i != Q)
output[ii++] = ITOC(i);
output[ii]='\0';
}
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