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The SBJ MVC Framework - The Model, from Abstraction to Realization

, 20 Mar 2009
A Model-View-Controller Framework that integrates with the MFC Doc/View architecture
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#include "stdafx.h"
#include "PasswordUtils.h"

#include <stdlib.h>

const int       NUM_FILLER_CHARS   = 8;
const CString   s_strFillerChars   = _T("SLWMTQYP");
const CString   s_strPossibleChars = _T("0123456789ABCDEFSLWMTQYP");

// local functions
namespace PasswordUtilsLocals
{
	void MakeLength(int nTargetLen, CString& rString);
	long RandomNumber(int nMin, int nMax);
	bool FindIllegalChars(CString& rStrKey);
	void RemoveFillers(CString& rStrKey);
	int  HexStrToInt(const TCHAR *value);
}

void
SbjCore::PasswordUtils::EncryptDate(
  int     nMonth,   // [in]  month
  int     nDay,     // [in]  day
  int     nYear,    // [in]  year
  int     nType,    // [in]  type of password, defined by calling app
  CString& rStrKey) // [out] resulting password
{
	// Seed the random number generator with system time
	CTime t = CTime::GetCurrentTime();
	UINT nTime = static_cast<UINT>( t.GetTime() );
	srand( nTime );

	//for(int i = 0; i < 100; i ++)
	//{
    //	TRACE(_T("%d\n"), EncryptPasswordLocals::RandomNumber(0, NUM_FILLER_CHARS - 1) );
	//}

	// multiply by 100
	long nBigDay   = nDay * 100;
	long nBigMonth = nMonth * 100;
	long nBigYear  = (nYear - 2000) * 100;

	// Get string versions in hex
	CString strDay;
	strDay.Format(_T("%X"), nBigDay);

	CString strMonth;
	strMonth.Format(_T("%X"), nBigMonth);

	CString strYear;
	strYear.Format(_T("%X"), nBigYear);

	// Pad with filler characters to make it 6 chars long
	PasswordUtilsLocals::MakeLength(6, strDay);
	PasswordUtilsLocals::MakeLength(6, strMonth);
	PasswordUtilsLocals::MakeLength(6, strYear);

	// Now reverse each string and concatenate with dashes
	rStrKey.Format(_T("%s-%s-%s-"), strYear.MakeReverse(), strDay.MakeReverse(), strMonth.MakeReverse());

	// Get a 5 digit random number to use for the "type" section
	long n5dig = PasswordUtilsLocals::RandomNumber(10001, 99990);

	CString strTypeSection;
	strTypeSection.Format(_T("%u"), n5dig);

	CString strTypeVal;
	strTypeVal.Format(_T("%u"), nType);

	// Insert the type value in the 4th position in the type string
	strTypeSection.Insert(3, strTypeVal);

	rStrKey += strTypeSection;
}

// --------------------  DecryptPassword  ---------------------
// Deciphers the password into a date.  nType is retuned as
// the same in passed into CreatePassword.  If the password
// cannot be deciphered, false is returned and all 'out' params
// are left unchanged.
// ------------------------------------------------------------
bool
SbjCore::PasswordUtils::DecryptPassword(
  LPCTSTR pPassword, // [in]  password to decipher
  int&    nMonth,    // [out] month
  int&    nDay,      // [out] day
  int&    nYear,     // [out] year
  int&    nType)     // [out] type, same value passed in to CreatePassword
{
	bool bSuccess = true;

	CString strKey(pPassword);

	// Verify length
	if(strKey.GetLength() != 27)
	{
		bSuccess = false;
	}
	// verify the dashes
	if(bSuccess)
	{
		if( strKey[6] != _TCHAR('-') || strKey[13] != _TCHAR('-') || strKey[20] != _TCHAR('-') )
		{
			bSuccess = false;
		}
	}

	// parse out the four strings
	CString strDay;
	CString strMonth;
	CString strYear;
	CString strType;

	strYear  = strKey.Left(6);
	strDay   = strKey.Mid(7, 6);
	strMonth = strKey.Mid(14, 6);
	strType  = strKey.Mid(21, 6);

	// verify only legal characters exist
	if(bSuccess)
	{
		if( PasswordUtilsLocals::FindIllegalChars(strDay)  ||
			PasswordUtilsLocals::FindIllegalChars(strMonth)||
			PasswordUtilsLocals::FindIllegalChars(strYear) ||
			PasswordUtilsLocals::FindIllegalChars(strType)    )
		{
			bSuccess = false;
		}
	}

	// reverse the strings and remove the filler characters
	if(bSuccess)
	{
		strDay   = strDay.MakeReverse();
		strMonth = strMonth.MakeReverse();
		strYear  = strYear.MakeReverse();

		PasswordUtilsLocals::RemoveFillers(strDay);
		PasswordUtilsLocals::RemoveFillers(strMonth);
		PasswordUtilsLocals::RemoveFillers(strYear);

		// What is left at this point is a hex version of the month, day and year
		// still multiplied by 100.

		// Convert it back to decimal numbers
		_stscanf_s (strDay,_T("%x"), &nDay);
		_stscanf_s (strMonth,_T("%x"), &nMonth);
		_stscanf_s (strYear,_T("%x"), &nYear);

		// Divide it back by 100
		nDay /= 100;
		nMonth /= 100;

		// The year used a 2 digit format, so it gets 2000 added on
		nYear = nYear/100 + 2000;

		// Extract the type from its string
		CString strTypeVal(strType[3]);
		nType = atoi(strTypeVal);
	}

	return bSuccess;
}

void
PasswordUtilsLocals::MakeLength(int nTargetLen, CString& rString)
{
	int nLen = rString.GetLength();
	int nPos = 0;
	while(nLen < nTargetLen)
	{
		int nIndex = PasswordUtilsLocals::RandomNumber(0, NUM_FILLER_CHARS - 1);
		nLen = rString.Insert( nPos, s_strFillerChars.GetAt(nIndex) );
		nPos += 2;
	}
}

long
PasswordUtilsLocals::RandomNumber(int nMin, int nMax)
{
	// Get the random number
	double dRanNum = static_cast<double>( rand() );

	// convert it to a range
	double dRandMax  = static_cast<double>(RAND_MAX) + 1.0;
	double dMaxRange = static_cast<double>(nMax);
	double dMinRange = static_cast<double>(nMin);
	int n = static_cast<int>( dRanNum / dRandMax * (dMaxRange - dMinRange) + dMinRange );

	return n;
}

bool
PasswordUtilsLocals::FindIllegalChars(CString& rStrKey)
{
	bool bInvalid = false;
	int nLen = rStrKey.GetLength();

	for(int i = 0; i < nLen; i ++)
	{
		if( s_strPossibleChars.Find(rStrKey.GetAt(i)) == -1 )
		{
			bInvalid = true;
			break;
		}
	}

	return bInvalid;
}

void
PasswordUtilsLocals::RemoveFillers(CString& rStrKey)
{
	CString strTemp(rStrKey);

	rStrKey.Empty();

	int nLen = strTemp.GetLength();
	for(int i = 0; i < nLen; i ++)
	{
		// If it's not a filler add it into the string
		if( s_strFillerChars.Find(strTemp.GetAt(i)) == -1 )
		{
			rStrKey += strTemp.GetAt(i);
		}
	}
}

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License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

About the Author

SBJ

United States United States
Real name is Steve Johnson. Programming since 1979. Started on a Heathkit Micro with a DEC LSI-11 and UCSD Pascal. Moved to PCs & DOS as soon as Turbo Pascal became available. Did some Assembly, ISR, TSR etc. All this while working for a Manufacturing Co. for 8 years. Had my own solo Co. doing barcode labeling software for 4 years (terrible business man, all I wanted to do was code). Since then working for various software companies. Moved to Windows around the time of 3.1 with Borland C then C++. Then on to VC++ and MFC, and just about anything I could get my hands on or had to learn for my job, and been at it ever since. Of course recently I've been playing with .NET, ASP, C#, WPF etc.

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