Re: Get ASCII value for character when higher than 127

On Tue, 05 Jun 2007 15:31:22 GMT, MrAsm <mrasm@usa.com> wrote:


....or maybe you are writing your crypted data as simple Ascii strings
and not in binary file format, so maybe you don't have the \n
conversion problem.

However, this is my C++ and C# code, that works.

<CODE language="C++">
// Crypt a string using XOR.
// The result is stored into a char-array.
// The string terminating NUL character
// is not crypted and is not copied into the
// destination array.
typedef std::vector< char > CharArray;
CharArray XorStringCrypt( const std::string & value, const std::string
& key )
{
    if ( value.empty() )
        throw std::invalid_argument(
            "XorStringCrypt: Input array is empty" );

    if ( key.empty() )
        throw std::invalid_argument(
            "XorStringCrypt: Key string is empty" );

    CharArray result;
    result.resize( value.length() );
    
    const size_t valueLengtht = value.length();
    const size_t keyLength = key.length();
    size_t keyIndex = 0;

    for ( size_t i = 0; i < valueLengtht; i++ )
    {
        result.at(i) = value.at(i) ^ key.at(keyIndex);

        keyIndex++;
        if ( keyIndex == keyLength )
            keyIndex = 0;
    }

    return result;
}

 //
 // TEST
 //

    std::string value = "11223AABBcH";
    std::string key = "Ciao";
    CharArray result = XorStringCrypt( value, key );
    
    // Save in binary mode (ios_base::binary),
    // to avoid conversion from 0x0A to 0x0D 0x0A
    std::ofstream out(
        "n:\\crypt.test",
        std::ios_base::out | std::ios_base::binary
    );
    for ( CharArray::const_iterator it = result.begin(); it !=
result.end(); ++it )
    {
        out.put( *it );
    }
    
</CODE>

<CODE language="C#">
// Apply XOR to an array
private static byte[] XorArrayCrypt(byte[] encrypted, byte[] key)
{
    byte[] decrypted = new byte[ encrypted.Length ];

    int k = 0;
    int i = 0;
    for ( i = 0; i < encrypted.Length; i++ )
    {
        decrypted[i] = (byte) (encrypted[i] ^ key[k]);

        k++;
        if (k == key.Length)
            k = 0;
    }

    return decrypted;
}

// Decrypt a string stored in encrypted byte array, using XOR
private static string XorDecrypt(byte[] encrypted, string key)
{
    UTF8Encoding encoding = new UTF8Encoding();

    byte[] keyBytes = encoding.GetBytes(key);
    byte[] decryptedBytes = XorArrayCrypt(encrypted, keyBytes);

    return encoding.GetString(decryptedBytes);
}

/// <summary>
/// Test decrypt
/// </summary>
private void button1_Click(object sender, EventArgs e)
{
    // Read file data into memory
    FileStream inputFile = new FileStream(
                              @"N:\crypt.test",
                              FileMode.Open);
    int bytesCount = (int)inputFile.Length;
    byte[] byteArray = new byte[bytesCount];
    inputFile.Read(byteArray, 0, bytesCount);
    inputFile.Close();

    string decrypted = XorDecrypt(byteArray, "Ciao");
    MessageBox.Show(decrypted);
}
</CODE>

MrAsm