encryption/decryption errors

[Xakzi]

Hello!

I am working on a small decryption / encryption program using Win32 Console Application c++

nothing big, here is my code:

#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <conio.h>
#include <stdio.h>

using namespace std;



int _tmain(int argc, _TCHAR* argv[])
{
    char name[100],target[100],ch,mod;                             //Declare Variables
    unsigned char apostrophe;
    int num[100],i,option;

    cout<<"Enter Your Option " << endl;
    cout<<"1. To Encrypt The File " << endl;
    cout<<"2. To Decrypt The File " << endl;
    cout<<"Option : ";
    cin>>option;

    if(option==1)
    {

        cout<<"Enter The Path Of A File Which Is To Be Encrypted : ";
        cin >> name;

        ifstream fin(name,ios::binary);                              //Open The Input File In A Binary Mode
        if(!fin)
        {                                                          //Show Error Occur If File Does Not Exist
            cout<<"Error In Openinig Of A File : ";                       //Or Any Error Occurs
            return 1;
        }

        cout<<"Enter The New Encrypted File Name : ";
        cin >> target;

        ofstream fout(target,ios::binary);                         //Open The OutPut File In A Binary Mode
        if(!fout)
        {
            cout<<"Error In Opening Of Target File : ";            //Show Error If Any Error Occrs In Opening Of A File
            return 1;
        }

        for(i=0;i<9;i++)
        {                                                         //Multiple For Loops For Storing The Numbers
            num[i]=i;                                                //In An Array
        }

        for(i=14;i<31;i++)                                         //Loops Will Store 100 Numbers
        {
            num[i-5]=i;                                              //Which Will Encrypt The Contents Of A File
        }

        for(i=33;i<=68;i++)                                        //To Avoid  The Error Ocuur Caused By The
        {                                                         //Enter Key , Tab Key & Space Key
            num[i-7]=i;                                              //These Variations In Loops Is Made
        }

        for(i=97;i<=122;i++)
        {
            num[i-35]=i;
        }

        while(fin)
        {                                                       //Open The Input File
            fin.get(ch);

            if(ch==EOF)break;                                       //Exit To Loop When End Of File

            if((ch>=97) && (ch<=122))
            {                                                     //Encrypt The Small Letters
                i=97;
                mod=num[ch-i];
                fout<<mod;
            }

            if((ch>=65) && (ch<=90))
            {
                i=39;                                                 //Encrypt The Capital Letters
                mod=num[ch-i];                                        //And Store In An Output File
                fout<<mod;
            }

            if((ch>=48) && (ch<=57))
            {
                i=4;                                                //Encrypt The Numbers
                mod=num[ch+i];
                fout<<mod;
            }

            if((ch==10)||(ch==13))
            {
                mod=ch;                                             //For Enter Key 
                fout<<mod;
            }

            if(ch==32)
                fout<<ch;                                             //For Space Key

            if(ch==9)
                fout<<ch;                                             //For Tab Key

            if(apostrophe==130)
                fout<<apostrophe;                             // é

            if((ch>=33)&&(ch<=47))
            {                                                    //For Special Symbols
                mod=ch+64;
                fout<<mod;
            }

            if((ch>=58)&&(ch<=64))
            {                                                    //For Special Symbols
                mod=ch+54;
                fout<<mod;
            }

            if((ch>=91)&&(ch<=96))
            {
                mod=ch+28;                                          //For Special Symbols
                fout<<mod;
            }

            if((ch>=123)&&(ch<=126))
            {
                mod=ch-40;                                          //For Special Symbols
                fout<<mod;
            }
        }

        fin.close();                                          //Close The Input File
        fout.close();                                         //Close The Output File

        cout<<"Your File Is Encrypted Now........... ";
        getch();
        return 0;
    }




    /*========================================================================
    =======================================*/


    /* This Program Will Decrypt The Document */


    if(option==2)
    {
        char name[30],target[30],ch,mod;                             //Declare Variables
        int num[100],i,flag;

        cout<<"Enter The Path Of A File Name Which Is To Be Decrypted : ";
        cin >> name;

        ifstream fin(name,ios::binary);
        if(!fin)                                                     //Open The Encryped File In A Binary Mode
        {
            cout<<"Error In Opening Of A File : ";
            return 1;                                                    //Show Error If File Does Not Exist
        }                                                            //Or Any Occurs In Opening Of A File

        cout<<"Enter The New Decrypted File Name : ";
        cin >> target;

        ofstream fout;
        fout.open(target,ios::binary);                              //Opens The Output File In An Binary Mode
        if(!fout)
        {                                                          //Show Error If Any Error Occurs In Opening Of A File
            cout<<"Error In Opening Of A Target File : ";
            return 1;
        }

        for(i=0;i<9;i++)
        {                                                          //Same Multiple For Loops For Storing The Numbers
            num[i]=i;                                                 //In An  Array
        }

        for(i=14;i<31;i++)
        {
            num[i-5]=i;                                               //Loops Will Store 100 Numbers
        }

        for(i=33;i<=68;i++)                                         //Which Encrypts The Document Also Decrypt It
        {
            num[i-7]=i;
        }

        while(fin)
        {                                                           //Opens The Encryped File
            fin.get(ch);
            flag=0;                                                        //Turn Off Flag
            if(ch==EOF)break;

            for(i=26;i<52;i++)
            {
                if(ch==num[i])                                            //Loop For Match The Small Letters Letters
                {
                    mod=i+39;                                                //If Match  Then Put Appropriate Letter
                    fout<<mod;                                               //In A OutPut File
                    flag=1; break ;                                             //Turn On Flag And Exit The Loop
                }
            }

            if (flag==1) continue ;                                        //If  Flag Is On Then Continue Outer Loop

            for(i=0;i<26;i++)
            {                                                          //Loop For Match The Capital Letters
                if(ch==num[i])
                {                                                        //If Match Then Put Appropriate Letter
                    mod=i+97;                                               //In A OutPut File 
                    fout<<mod;
                    flag=1;break;                                              //Turn On Flag And Exit From This Loop
                }
            }

            if (flag==1) continue ;                                       //If Flag Is On Then Continue Outer Loop

            for(i=52;i<62;i++)
            {                                                         //Loop For Numerical Numbers
                if(ch==num[i])
                {
                    mod=i-4;
                    fout<<mod;
                    flag=1; break ;
                }
            }

            if (flag==1) continue ;

            if((ch==10)||(ch==13))
            {
                mod=ch;                                             //Condition For Enter Key
                fout<<mod;
            }

            if(ch==32)
                fout<<ch;                                             //Condition For Space Key

            if(ch==9)
                fout<<ch;                                             //Condition For  Tab Key

            if(apostrophe==130)
                fout<<apostrophe;                                 //é

            if((ch>=97)&&(ch<=111))
            {
                mod=ch-64;                                          //For Special Symbols
                fout<<mod;
            }

            if((ch>=112)&&(ch<=118))
            {
                mod=ch-54;                                         //For Special Symbols
                fout<<mod;
            }

            if((ch>=119)&&(ch<=124))
            {
                mod=ch-28;                                         //For Special Symbols
                fout<<mod;
            }

            if((ch>=83)&&(ch<=86))
            {                                                   //For Special Symbols
                mod=ch+40;
                fout<<mod;
            }

        }

        fin.close();                                        //Close The EncryptedFile
        fout.close();                                       //Close Your OriginalDecrypted File

        cout<<"The File Is Being Decrypted............ ";
        getch();
        return 0;
    }

    return 0;
}

How the program works:
choose to encrypt:
you write in the file you want to encrypt, then choose new name for the encrypted file..
choose to decrypt:
you write in the encrypted file name, then choose new name for the decrypted file..

so my problems are following:

Apostrophe e's ( é ) and Apostrophe's ( ´ ) Gets deleted when I decrypt. (which I have in a txt file)

Also when I decrypt, the last character is written 2 times extra.

How can I fix those problems?

Sincerely~

[tinstaafl]

Apostrophe e's ( é ) and Apostrophe's ( ´ ) Gets deleted when I decrypt. (which I have in a txt file)

'apostrophe' is declared and used but never set, changing it to 'ch' in your if statement should correct that.

On a side note, You might be overthinking this a bit. Since your are using binary streams, there really is no need handle special characters and enter key , etc.. You shouldn't want your decrypted file to be easily displayed. Consider how the following simplifies things:

#include "stdafx.h"
#include <iostream>
#include <fstream>
#include <conio.h>
#include <stdio.h>
using namespace std;


int _tmain(int argc, _TCHAR* argv[])
{
    char name[100],target[100],ch,mod; //Declare Variables
    char key = 97;
    int option;
    cout<<"Enter Your Option " << endl;
    cout<<"1. To Encrypt The File " << endl;
    cout<<"2. To Decrypt The File " << endl;
    cout<<"Option : ";
    cin>>option;
    if(option==1)
    {
        cout<<"Enter The Path Of A File Which Is To Be Encrypted : ";
        cin >> name;
        ifstream fin(name,ios::binary); //Open The Input File In A Binary Mode
        if(!fin)
        { //Show Error Occur If File Does Not Exist
            cout<<"Error In Openinig Of A File : "; //Or Any Error Occurs
            _getch();
            return 1;
        }
        cout<<"Enter The New Encrypted File Name : ";
        cin >> target;
        ofstream fout(target,ios::binary); //Open The OutPut File In A Binary Mode
        if(!fout)
        {
            cout<<"Error In Opening Of Target File : "; //Show Error If Any Error Occrs In Opening Of A File
            _getch();
            return 1;
        }

        while(!fin.eof())
        { //Open The Input File
            fin.get(ch);
            mod = ch - key;
            if (mod < 0) mod += 256;
            fout << mod;
        }
        fin.close(); //Close The Input File
        fout.close(); //Close The Output File
        cout<<"Your File Is Encrypted Now........... ";
        _getch();
        return 0;
    }
    /*========================================================================
    =======================================*/
    /* This Program Will Decrypt The Document */
    if(option==2)
    {
        char ch,mod; //Declare Variables
        cout<<"Enter The Path Of A File Name Which Is To Be Decrypted : ";
        cin >> name;
        ifstream fin(name,ios::binary);
        if(!fin) //Open The Encryped File In A Binary Mode
        {
            cout<<"Error In Opening Of A File : ";
            _getch();
            return 1; //Show Error If File Does Not Exist
        } //Or Any Occurs In Opening Of A File
        cout<<"Enter The New Decrypted File Name : ";
        cin >> target;
        ofstream fout;
        fout.open(target,ios::binary); //Opens The Output File In An Binary Mode
        if(!fout)
        { //Show Error If Any Error Occurs In Opening Of A File
            cout<<"Error In Opening Of A Target File : ";
            _getch();
            return 1;
        }

        while(!fin.eof())
        { //Opens The Encryped File
            fin.get(ch);
            mod = ch + key;
            if ( mod > 255) mod -= 255;
            fout << mod;
        }
        fin.close(); //Close The EncryptedFile
        fout.close(); //Close Your OriginalDecrypted File
        cout<<"The File Is Being Decrypted............ ";
        _getch();
        return 0;
    }
    return 0;
}

[Xakzi]

It is true that this is easier to encrypt, but changing the whole content of a txt file the same way with one kind of "key" is not that hard to "crack"

Ofcourse it doesn't need to be hard encrypted but I wouldn't want it easily decrypted..

But, if there is no other way to find an easier fix to what I already started with, I guess this is what I would have to go with..

I will leave this thread open IF someone can find a fix for the code I used, that would be swell..

But for now.. I thank you big time tinstaafl :)

[kill-it]

You may have to try the RSA algorithm whcih is a project am working on now