Help with my encryption program

This is a discussion on Help with my encryption program within the C++ Programming forums, part of the General Programming Boards category; Hey can someone help out here so it can encrypt and decrypt, i've been trying to figure it for a ...

  1. #1
    Registered User quiksilver9531's Avatar
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    Help with my encryption program

    Hey can someone help out here so it can encrypt and decrypt, i've been trying to figure it for a while and I can encrypt but I can decrypt, help would be appreciated. Thanks

    CODE::

    cout<<"Enter something you want to encrypt: "<<endl;
    cin.get(user, 256);
    cin.ignore(80, '\n');
    string_length=strlen(user);

    do
    {
    user[x];
    l++; x++;
    }

    while(x!=string_length);

    cout<<endl;
    cout<<"Encrypted: "<<endl;
    cout<<endl;
    cout<<user<<endl;
    cout<<endl;
    cout<<"Press any key to continue"<<endl;
    int wait= getch();

    clrscr();

    cout<<"Would you like to decrypt it? 1 = yes / 0 = no"<<endl;
    cin >>user_choice;

    if (user_choice==1)
    {
    x=0; l=33;
    cout<<"Test"<<endl;
    do
    {
    user[x]=l;
    l--; x++;
    }

    while(x!=string_length);

  2. #2
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    do
    {
    user[x];
    l++; x++;
    }
    I don't get it. How does that encrypt anything?

  3. #3
    and the hat of wrongness Salem's Avatar
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    Code:
    do { 
       user[x]; 
       l++; x++; 
    }  while(x!=string_length);
    This doesn't do anything to user[x] - sure it reads it, but that's all.

    A most trivial encryption would be
    Code:
    do { 
       user[x]++; 
       x++; 
    }  while(x!=string_length);
    The decode for this would be
    Code:
    do { 
       user[x]--; 
       x++; 
    }  while(x!=string_length);

  4. #4
    Registered User quiksilver9531's Avatar
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    THanks, that worked

  5. #5
    Budding Synth Programmer samGwilliam's Avatar
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    Have two strings: a user plaintext string and a key string:

    Code:
    char user [31];   // 30 chars.
    char key [31];
    
    int userLength;
    int keyLength;
    int currentKeyByte = 0;
    
    cout << "Enter string: ";
    cin >> user;
    
    cout << "Enter key: ";
    cin >> key;
    
    userLength = strlen (user);
    keyLength = strlen (key);
    
    for (i = 0; i < userLength; i++)
    {
       user [i] ^= key [currentKeyByte];
       currentKeyByte++;
    
       currentKeyByte %= keyLength;
    }
    or something.

  6. #6
    Registered User quiksilver9531's Avatar
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    Exclamation

    Salem:

    do {
    user[x]++;
    x++;
    } while(x!=string_length);


    This works but how can I make it so it doesnt just increase the decimal of the ASCII by 1, I want to make it, for example, double and then divide or something to make it a complicated encryption.

    Thanks

  7. #7
    Registered User
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    well
    you can do

    user[x] += 2 to add 2 but that is no very strong encryption, I suggest you use a key and 'mix up' the bits (^=) like samGwilliam already said.

  8. #8
    ¡Amo fútbol!
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    is the %= operator equal to a=a%b

  9. #9
    and the hat of wrongness Salem's Avatar
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    > This works but how can I make it so it doesnt just increase the decimal of the ASCII by 1

    In general, you have
    &nbsp;&nbsp;&nbsp;&nbsp;user[x] = encrypt(user[x]);

    You can make encrypt anything you want, the only restriction is that it is a reversible process (the reverse is decrypt).

    So adding 1 has an obvious inverse which is subtract 1

    The rest is down to your imagination, and creating a pair of functions called encrypt() and decrypt() which mirror one another

  10. #10
    Budding Synth Programmer samGwilliam's Avatar
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    I made a file encryption program. The encrypt and decrypt functions are referenced by a pointer. The address of this is decided before the loop so as to avoid an if statement every iteration, just one outside it.

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