*/


//Includes
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <windows.h>

//Macros
#define MAX_SIZE 150
#define SLEEP_TIME 5000

//Global variable (cypher key)
char *m_key = "FILEZILLA1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ";


//PRE:  decimal values representing ASCII chars,
//              every three digits becomes one ASCII char
//              e.g.:   042040063063
//POST: ASCII chars are copied back to buff[]
//              e.g.:   *(??
//              the length of the new string is returned
int digit2char(char buff[])
{
        char tmp_buff[4], ascii_buff[MAX_SIZE];
        unsigned int i=0, j=0, n=0, len=(strlen(buff)/3);
        for(i=0,j=0;i<strlen(buff);i+=3,++j)
        {
                tmp_buff[0]=buff[i];
                tmp_buff[1]=buff[i+1];
                tmp_buff[2]=buff[i+2];
                tmp_buff[3]='\0';

                n=atoi(tmp_buff);
                ascii_buff[j]=(char)n;
        }
        ascii_buff[j]='\0';
        printf("ascii_buff:%s\n", ascii_buff);
        strcpy(buff, ascii_buff);

        return len;
}

//PRE: buffer containing ASCII chars of cypher
//     (rather than their numberic ASCII value)
//POST:length of cleartext password is returned
unsigned int decrypt(char buff[])
{
        unsigned int i, pos, len;

        len=digit2char(buff);
        pos=len%strlen(m_key);

        for (i=0;i<len;i++)
                buff[i]=buff[i]^m_key[(i+pos)%strlen(m_key)];

        return len;
}

int main(void)
{
        char cypher[MAX_SIZE];
        unsigned int len=0,i=0;

        printf("Enter cypher (encrypted password)\ne.g.:
120125125112000\n->");
        scanf("%s", cypher);
        if(strlen(cypher)%3==0)
        {
                len=decrypt(cypher);
                printf("cleartext password:");
                for(i=0;i<len;++i)
                        printf("%c",cypher[i]);
                printf("\n");
        }
        else
        {
                printf("You didn't enter a valid cypher!\n");
                printf("It should be a numeric value whose length is multiple of
3\n");
        }

        printf("Ending program in %d seconds...\n", SLEEP_TIME/1000);
        Sleep(SLEEP_TIME);
        return 0;
}