main.c

Basic test of Vigenere s Algorithm

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "utilities2.h"
#include "utilities.h"

#define ENCODING 0
#define DECODING 1
#define MIN 3
#define MAX 7
#define N 10



char *caesar (char *p,char k,int sizeOfP,int codingMode);
char *vigenere (char *p,char *k,int sizeOfP,int codingMode);
char bruteCaesar(char* code);
char freqAnalysis(char *code);
int* distances (char* code);


int main(){

    char *code = getText("code2.txt");
    int *dists=distances(code);
    int i=0;
   // for (i=0;i<150;i++){printf("\n[%i]: %i",i,dists[i]);}

    int * N_sorted_dists = sortArray(  dists,strlen(code)+2  ,N); // 2.

    // *dists mit 0en initialisieren


/*ggT der N abstaende aus N_sorted_dists berechnen*/

int ggT = 0;
int hggT = 2;

printf("\n\n %i -- \n",N_sorted_dists[2]);

ggT = euklid(N_sorted_dists[1],N_sorted_dists[0]);


    while(hggT < N){
        printf("\nx: %i",N_sorted_dists[hggT]);
        printf("--%i\n",ggT);
        ggT = euklid(N_sorted_dists[hggT],ggT);
        hggT++;
    }


/*Haeufigkeitsanalyse bzgl. ggT (muss nicht als Fkt. implementiert sein. Kann auch in main() gemacht werden*/
    char key[ggT];
    char help[strlen(code)];
    int j, k;

    for(i = 0; i < ggT; i++) {
        k = 0;
        j = i;
        while (j <= strlen(code)) {
            help[k] = code[j];
            k++;
            j += ggT;
        }
        help[k] = '\0';
        key[i] = freqAnalysis(help);
    }

    key[ggT]='\0';
    printf("\n\nKey: %s\n",key);

/*Decodierung mit dem gefunden Schlüssel und abschließendes Abspeichern*/
    char *decoded = vigenere(code,key,strlen(code)+1,DECODING);
    puts("Entschluesselt:\n");
    printf("\n%s",decoded);
    //writeText(decoded,"plaintext.txt");

/*Saubermachen*/
    free(N_sorted_dists);
    free(decoded);
    free(code);


    return 0;
}

int* distances (char* code){
    /*Hier gehts los*/
    int i = MIN, j = 0, k=0, abstand = 0;
    char *sub,  *pos=NULL;
    int *hauf;

    hauf = (int*) calloc(strlen(code)+2,sizeof(int));
    sub = (char*) malloc(MAX*sizeof(char));

    while(i < MAX){
        for ( j = 0; j < strlen(code); j++){
            for(k=0;k<i;k++)
                sub[k] = code[j+k];


            sub[k] = '\0';

            pos = strstr(code+j+1,sub);


            if(pos!=NULL){

                abstand = pos - (code+j);

                hauf[abstand]++;
                printf("- %i -- hauf: %i\n" , abstand, hauf[abstand]);
            }

        }
        i++;
    }
    free(sub);
    return hauf;

}


/*Die vier Funktionen aus dem Betreuten Programmieren*/


char *caesar (char *p,char k,int sizeOfP,int codingMode)
{
    char *c = (char*)malloc(sizeOfP*sizeof(char));
    k=k-'A';
    int i=0;
    if(codingMode==ENCODING)
    {
        while (*(p+i)!='\0')
        {
            if((*(p+i))+k>'Z')
                *(c+i) =  ((*(p+i))+k)-('Z'+1) + 'A';
            else
                *(c+i) = (*(p+i))+k;
            i++;
        }
    }
    else if(codingMode==DECODING)
    {
        while (*(p+i)!='\0')
        {
            if((*(p+i))-k<'A')
                *(c+i) = 'Z' - ('A'-((*(p+i))-k)-1);
                //*(c+i) = 'Z' - ('A'-(*(p+i)-(*(k+j)-'A'))-1);
            else
                *(c+i) = (*(p+i))-k;
            i++;
        }
    }
    else
        return NULL;



 (*(c+i))='\0';
 return c;
}

char *vigenere (char *p,char *k,int sizeOfP,int codingMode)
{
    char *c = (char*)malloc(sizeOfP*sizeof(char));
    int i=0,j=0;
    if(codingMode==ENCODING)
    {
        while (*(p+i)!='\0')
        {
        if((*(p+i))+((*(k+j))-'A')>'Z')
            *(c+i) =  ((*(p+i))+((*(k+j))-'A'))-('Z'+1) + 'A';
        else
            *(c+i) = (*(p+i))+((*(k+j))-'A');
        i++;
        if((*(k+j+1))!='\0')
            j=j+1;
        else
            j=0;
        }
    }
    else if(codingMode==DECODING)
    {
        while (*(p+i)!='\0')
        {
            if((*(p+i))-((*(k+j))-'A')<'A')
                *(c+i) = 'Z' - ('A'-(*(p+i)-(*(k+j)-'A'))-1);
            else
                *(c+i) = (*(p+i))-((*(k+j))-'A');
            i++;
            if((*(k+j+1))!='\0')
                j=j+1;
            else
                j=0;
        }
    }
    else
        return NULL;

 (*(c+i))='\0';
 return c;
}

char bruteCaesar(char* code)
{
    int isGood=0;
    char k=64;
    char *p;
    int i;
    while(isGood==0)
    {
        k++;
        if(k>'Z')
            return 0;
        p=caesar(code,k,strlen(code)+1,DECODING);
        printf("\n");
        for(i=0;i<20;i++)
            printf("%c",p[i]);
        printf("\nSchlüssel: %c",k);
        printf("\nWenn der Schlüssel passt mit 1 bestätigen oder 0 ablehnen: ");
        scanf("%i",&isGood);
    }
    return k;
}

char freqAnalysis(char *code)
{
    int counter[26];
    int i,max=0,maxind=0;
    for(i=0;i<26;i++)
        counter[i]=0;
    while(*(code+i)!='\0')
    {
                counter[*(code+i)-65]++;
                i++;
    }
    for(i=0;i<26;i++)
    {
        if(counter[i]>max)
        {
            max=counter[i];
            maxind=i;
        }
    }
    return (char)65+((26+(maxind-4))%26);
}