crypt.c

#include <stdio.h>
#include <stdlib.h>

int main(int argc,char *argv[])
{
    FILE *source;
    FILE *locked;
    int x;
    int zwspeicher;
    char string[64]="";
    switch(argc)
    {
        case 1:
            do
            {
                printf("Original file: ");
                gets(string);
                source=fopen(string,"rb");
            } while(source==NULL);
            printf("Do you want a named outputfile(y/n) ");
            switch(getchar())
            {
                case 'Y':
                case 'y':
                    printf("\nFilename: ");
                    gets(string);
                    locked=fopen(string,"w+b");
                    break;
                default:
                    sprintf(string,"%s.lck",argv[1]);
                    locked=fopen(string,"w+b");
                    break;
            }
            break;
        case 2:
            source=fopen(argv[1],"rb");
            if(source==NULL)
            {
                printf("File does not exist!\n");
                return -1;
            }
            else
            {
                for(x=0;x<60 && argv[1][x]!='.';x++)
                {
                    string[x]=argv[1][x];
                }
                sprintf(string+x,".lck");
                locked=fopen(string,"w+b");
            }
            break;
        case 3:
            source=fopen(argv[1],"rb");
            if(source==NULL)
            {
                printf("File does not exist!\n");
                return -1;
            }
            else
            {
                locked=fopen(argv[2],"w+b");
                if(locked==NULL)
                {
                    printf("File does not exist!\n");
                    return -1;
                }
            }
            break;
        default:
            printf("Error\n");
            return -1;
            break;
    }
    fseek(source,-1L,SEEK_END);
    while(fread(string,1,1,source) && ftell(source)>1)
    {

        for(x=1,string[0]=(char)~string[0],zwspeicher=0;x<=128;x*=2)
        {
            zwspeicher+=(string[0]/x%2)*x;
        }
        sprintf(string,"%c",zwspeicher);
        fwrite(string,1,1,locked);
        fseek(source,-2L,SEEK_CUR);
    }
    string[0]=(char)~string[0];
    fwrite(string,1,1,locked);
    fclose(source);
    fclose(locked);
    return 0;
}