Interview Preparation - C / C++ / MFC Discussion Boards

jkirkerx19-Dec-11 10:53

19-Dec-11 10:53

It came from a Microsoft MSDN description of CryptImportKey, saying that either use CryptDeriveKey, Gen Key or import Key.

I tried it because I was not able to use my existing key format in CryptImportKey, and it expected a Key Blob. So I just wanted to see if I could create a key without using CryptCreateHash.

Well it loads without error, the call to DES is suppose to be in the blob header I think. The key is not right but I did create a key without CryptCreateHash.

Perfect Match!

jkirkerx19-Dec-11 12:13

jkirkerx

19-Dec-11 12:13

Perfect Match!, on the buffer value, and the base64 output. This is the framework for duplicating the asp.net DES and 3DES.

I need to clean it up, secure it, and take out the garbage to finalize it.

WOW, what a long journey, Thank you very much Dave for helping me out, and standing by my side during the journey, and not giving up on me.

// Link with the Advapi32.lib file.
#pragma comment (lib, "advapi32")
#pragma comment(lib, "crypt32.lib")
	
	BYTE DesKeyBlob_64[] = {
    0x08,0x02,0x00,0x00,0x01,0x66,0x00,0x00,	// BLOB header 
    0x08,0x00,0x00,0x00,						// key length, in bytes
    0x2a,0x10,0x5D,0x9C,0x4E,0x4,0xDA,0x20		// DES key with parity
    };	
		
WCHAR*	_encrypt_DES( WCHAR *pzInputW )
{
	BOOL			bResult = FALSE;
	WCHAR			*szOutput = NULL;
 
	HCRYPTPROV		hProv;
	HCRYPTKEY		hKey;
	ALG_ID			Algid;
	PBYTE			pbKeyBlob = NULL; 
    DWORD			dwKeyBlobLen;	
	BYTE			*pbBuffer;
	DWORD			dwBlockLen = 0;
	DWORD			dwDataLen = 0;
	DWORD			errorCode = 0;
	DWORD			cbData = 0;
	BOOL			bFinal = TRUE;
	 
	// Get the size of the conversion first
	int iCharA = WideCharToMultiByte(CP_UTF8, 0, pzInputW, -1, NULL, 0, NULL, NULL);	
	char *szInputA = new char[iCharA];
	WideCharToMultiByte(CP_UTF8, 0, pzInputW, -1, szInputA, iCharA, NULL, NULL);
			
	// Aquire a handle to the Encryption provider
	bResult = CryptAcquireContextW( &hProv, 0, MS_ENHANCED_PROV, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT);
	// hProv - Set the Key
	bResult = CryptImportKey(hProv, DesKeyBlob_64, sizeof(DesKeyBlob_64), 0, CRYPT_EXPORTABLE, &hKey);	
	// hProv - IV
	bResult = CryptSetKeyParam(hKey, KP_IV, IV_64, 0);	
	
	dwDataLen = sizeof(ALG_ID);
	cbData = sizeof(szInputA);	

	if (!CryptGetKeyParam(hKey, KP_ALGID, (BYTE *)&Algid, &dwDataLen, 0)) 
		return 0;
	
	if (GET_ALG_TYPE(Algid) != ALG_TYPE_STREAM) {		
		dwDataLen = sizeof(DWORD);		
		if (!CryptGetKeyParam(hKey, KP_BLOCKLEN, (BYTE *)&dwBlockLen, &dwDataLen, 0))
		  return 0;		
		dwDataLen = ((cbData + dwBlockLen - 1) / dwBlockLen) * dwBlockLen;		
		if (!(pbBuffer = (BYTE *)LocalAlloc(LMEM_FIXED, dwDataLen))) 
			return 0;
		} 
		else {
			if (!(pbBuffer = (BYTE *)LocalAlloc(LMEM_FIXED, cbData))) 
				return 0;
		}	  
		CopyMemory(pbBuffer, szInputA, cbData);
		if (!CryptEncrypt(hKey, 0, bFinal, 0, pbBuffer, &cbData, dwDataLen)) {
			DWORD dwError = GetLastError();		
			if(ERROR_MORE_DATA == dwError) {
				DWORD dwSizeNeeded = cbData;
				CopyMemory( pbBuffer, szInputA, cbData );
				bResult = CryptEncrypt(hKey, 0, FALSE, 0, pbBuffer, &dwSizeNeeded, dwDataLen);
			}			
			LocalFree(pbBuffer);
			return 0;
	}

	// Peek inside the buffer before Binary to String
	BYTE szByte[8];
	for (int i = 0; i < cbData; ++i) {
		szByte[i] = (BYTE)pbBuffer[i];
	}				
	
	DWORD dwResult = 0;
	TCHAR *szBase64 = NULL;		
	if(CryptBinaryToString((BYTE*)pbBuffer, 8, CRYPT_STRING_BASE64, NULL, &dwResult)) {		
		szBase64 = new TCHAR[dwResult];		
		CryptBinaryToString((BYTE*)pbBuffer, 8, CRYPT_STRING_BASE64, szBase64, &dwResult);			
		szOutput = (WCHAR*)szBase64;
		delete [] szBase64;
	}	

	// Secure sensitive data in buffers
	SecureZeroMemory( pbBuffer, sizeof(pbBuffer) );
	
	// Clean up the garbage in the heap
	delete [] szInputA;

	CryptDestroyKey(hKey);
	CryptReleaseContext(hProv, 0);	
	
	return szOutput;
}

Re: Perfect Match!

Randor 19-Dec-11 14:03

Randor

19-Dec-11 14:03

Hey Jim,

That is excellent news! Big Grin | :-D

Just in time for Monday night football too. Since your over there in Huntington Beach, CA would that make you a San Francisco 49ers fan or San Diego Chargers fan? I'll be pulling for the Pittsburgh Steelers tonight... because if San Francisco loses the New Orleans Saints will have a chance to gain the #2 NFC slot and obtain the bye week.

Best Wishes,
-David Delaune

Re: Perfect Match!

jkirkerx19-Dec-11 14:49

jkirkerx

19-Dec-11 14:49

Chargers Fan, but they should of kept Marty Schottenheimer. The current coach did nothing but get good players injured over the last few years (LT).

Pittsburgh is the luckiest team I've ever seen, or perhaps I should say conservative but effective.

Ben knows what to do to win games, and the EST factor, east coast team playing on west coast should not be an issue. Without the December mud of Heines field, should be a close game.

I have bowling tonight, but will try to catch parts of the game.

Re: DES Encryption

jkirkerx16-Dec-11 7:59

jkirkerx

16-Dec-11 7:59

That did fly way over my head.

So I don't need that line of code. I can just go straight to the next lines

bResult = CryptHashData(hHash, KEY_64, cbKey64, 0); <-- So this must be wrong as well
bResult = CryptDeriveKey(hProv, CALG_DES, hHash, 0, &hKey);
bResult = CryptSetKeyParam(hKey, KP_IV, IV_64, 0);

Symmetric-key - Initialization Vector

jkirkerx16-Dec-11 18:04

jkirkerx

16-Dec-11 18:04

My function works good, only I don't get the exact value or match I expect.

I read up on Initialization vector, and used CyrptSetKeyParam to add my IV, but this occurs in the background, and you can't really check it, to make sure that's what happened.

If the IV is just a prefix, that goes in front of the data to be encrypted, then is it common practice to skip the CryptSetKeyParam, and just prefix the data to be encrypted?

I remarked out the CryptSetKeyParam, and I did get different values returned in the buffer, but not enough to get the results I'm looking for.

If I experiment with it, then I need to write a whole new buffer routine that adds the extra space, and do new calculations.

Without:
I˜a‚ú|¢-Øø×"©¨Nþt¾dÃMN££Ð¢æÀDµ£N»£jŽg5„Äþti«L6±†à©Cþìü

With:
€&§¶Í>ªÈÇ3,í&%®•Ï¢?¾(ÞÆø0Ç6Ÿ§ìÆ·(õæd¢‡ôKFo{ü‘	(!ÛÏß·Èh‰¶

Re: Symmetric-key - Initialization Vector

C^hris L^osinger17-Dec-11 9:38

C^hris L^osinger

17-Dec-11 9:38

IV is not exactly a prefix.

basically an IV is a block of data that goes through the cipher before your data does, in order to set the internal state of the cipher to something other than the default. it differs from a simple prefix in that the IV should be unpredictable to potential eavesdroppers and should be chose anew for each message. in a way, it's a secondary key.

take a look at wiki[^]

image processing toolkits | batch image processing

Interview Preparation

pix_programmer15-Dec-11 18:23

pix_programmer

15-Dec-11 18:23

Can any one post some good links to C/C++ Interview questions that were asked in any of the MNC's?

Re: Interview Preparation

Chandrasekharan P15-Dec-11 22:07

Chandrasekharan P

15-Dec-11 22:07

there is a site which can give you all information. Click on this link [^]

Every new day is another chance to change your life.

memory leaking in playing video using DirectShow.

Le@rner14-Dec-11 23:48

Le@rner

14-Dec-11 23:48

Hi all,

#define SAFERELEASE( X ) { if( X ) { X->Release(); X = NULL; } }

HRESULT m_objHRsult;
IGraphBuilder* m_objGraphBuilder;
IMediaControl* m_objMediaControl;
IMediaEventEx* m_objMediaEvent;
IVideoWindow* m_objVideownd;
IMediaSeeking* m_objMediaSeeking;

m_objHRsult=CoCreateInstance(CLSID_FilterGraph,NULL,CLSCTX_INPROC_SERVER,IID_IGraphBuilder,(void**)& m_objGraphBuilder);
	
m_objHRsult=m_objGraphBuilder->QueryInterface(IID_IMediaControl,(void**)&m_objMediaControl);
m_objHRsult=m_objGraphBuilder->QueryInterface(IID_IMediaEventEx,(void**)&m_objMediaEvent);
m_objHRsult=m_objGraphBuilder->QueryInterface(IID_IVideoWindow,(void**)&m_objVideownd);
m_objHRsult=m_objGraphBuilder->QueryInterface(IID_IMediaSeeking,(void**)&m_objMediaSeeking);
m_objHRsult=m_objMediaEvent->SetNotifyWindow((OAHWND)main_Dlg->GetSafeHwnd(),WM_GRAPHNOTIFY,0);

m_objGraphBuilder->RenderFile(path,NULL);

m_objMediaControl->Run();

//now release all
if(m_objMediaControl)
		m_objMediaControl->Stop();

	// Release and zero DirectShow interfaces
    SAFERELEASE(m_objMediaEvent);
    SAFERELEASE(m_objMediaControl);
    SAFERELEASE(m_objVideownd);
    SAFERELEASE(m_objGraphBuilder);

//but still memory not rleasing that is occupyuing after RenderFile.

please help me for this.

thanks in advance.

Re: memory leaking in playing video using DirectShow.

CPallini15-Dec-11 1:39

CPallini

15-Dec-11 1:39

Why didn't you release the MediaSeeking interface?

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Re: memory leaking in playing video using DirectShow.

Le@rner15-Dec-11 17:47

Le@rner

15-Dec-11 17:47

ok not i release MediaSeeking interface also but there is some memory leak.

after RenderFile memory increase and not come down on previous positioin after releasing all interfaces.

Connecting to SQL CE from MFC Pocket PC 2003

Vieru Dorin14-Dec-11 21:10

Vieru Dorin

14-Dec-11 21:10

I wrote an application in Visual C++ language, mfc apllication (Dialog Based, MFC in static library), PocketPC 2003 SDK to connect to *.sdf file saved in my PocketPC device.
The same code, for Windows works. The SQL querries from my mfc-Windows affetcs *.sdf file witch is savd on My Computer. But if I wrote the same code for Pocket PC to affect a file witch is saved on device it has no effect.

The code is this:
// ADOWin7Dlg.cpp : implementation file
//

#include "stdafx.h"
#include "ADOWin7.h"
#include "ADOWin7Dlg.h"

#import <<c:\\program files\\common="" files\\system\\ado\\msado15.dll="">> rename( "EOF", "AdoNSEOF")

_bstr_t bstrConnect = "Provider=Microsoft.SQLSERVER.CE.OLEDB.3.5;Data Source=C:\\MyDatabase1.sdf;";

#ifdef _DEBUG
#define new DEBUG_NEW
#endif

-------------ussualy code generated by Visual Sdudio------------------

void CADOWin7Dlg::OnBnClickedButton1()
{
    ADODB::_ConnectionPtr pConn;

    pConn.CreateInstance(__uuidof(ADODB::Connection));

    pConn->Open(bstrConnect, "", "", 0);

    pConn->Execute("INSERT INTO Table1 (Nume) Values ('Arad')", NULL, NULL);
    pConn->Close();

}

I cann not understand why the code works on PC and the same code does not work on Pocket PC. If I run the *.exe file on Pocket PC does not appears any error or message. If I run Query Analyzer 3.5 what is installed on Pocket PC, and make an SQL querry from it, it affects my *sdf file from device. The SQL Compact Edition is installed on device.
Maybe is an ADO connection problem. I don't know.

Thanks for help.

modified 19-Dec-11 11:42am.

Re: Connecting to SQL CE from MFC Pocket PC 2003

Richard MacCutchan14-Dec-11 22:20

Richard MacCutchan

14-Dec-11 22:20

Adding some debug code, or at the very least, checking the return values from your function calls would probably give you some useful information.

Unrequited desire is character building. OriginalGriff
I'm sitting here giving you a standing ovation - Len Goodman

Library to solve optimization matrix

qwerty_201114-Dec-11 16:49

qwerty_2011

14-Dec-11 16:49

hello

I want to ask about the library for otimization matrix.
Anyone know about library for optimization matrix that can use in visual c++?
Because I need the library that can solve the optimization matrix like a cvx_solver library in matlab.

Thanks so much

Re: Library to solve optimization matrix

Stefan_Lang14-Dec-11 22:34

Stefan_Lang

14-Dec-11 22:34

Check out the links under http://en.wikipedia.org/wiki/Convex_optimization#Software

Re: Library to solve optimization matrix

qwerty_201115-Dec-11 16:30

qwerty_2011

15-Dec-11 16:30

After I read that link, I think all of the library is for matlab. But I need to solve the optimization matrix in visual c++. The sample matlab source that I want to solve in visual c++ is

cvx_begin
    variable x(n)
    minimize( norm( A * x - b, 2 ) )
    subject to
        C * x == d
        norm( x, Inf ) <= e
cvx_end

Anyone know the library for visual c++ to solve that problem?
Thank you

Re: Library to solve optimization matrix

Stefan_Lang15-Dec-11 22:31

Stefan_Lang

15-Dec-11 22:31

There are several links, and while some of the links offered there imply the inclusion of matlab, others don't. I haven't checked any, I just did a quick search on google and this seemed the most promising one for software solutions not including matlab. I've found one other link that pointed to Wolfram Alpha Mathematica instead - but I thought if you don't want matlab, then maybe Mathematica is not an option either.

Use the environment provided by the application instead from system environment.

Member 848801414-Dec-11 16:12

Member 8488014

14-Dec-11 16:12

SQL

How to tell the OS to use the environment provided by the WinForm application instead from system environment.

Example : My WinForm application uses C++ runtime dll's(msvcm80.dll, msvcp80.dll and msvcr80.dll) and bundling them as part of the application. How to make sure that my application will use the C++ runtime dll's that bundled along with product even though the dll's present else where in the system(c:\Windows\Winsxs).

Regards,
Gopal Reddy

Re: Use the environment provided by the application instead from system environment.

kakan15-Dec-11 0:05

kakan

15-Dec-11 0:05

Put the dll's in the same directory as your app.

See here:
http://msdn.microsoft.com/en-us/library/windows/desktop/ms682586(v=vs.85).aspx[^]

Alcohol. The cause of, and the solution to, all of life's problems - Homer Simpson

Re: Use the environment provided by the application instead from system environment.

Randor 15-Dec-11 5:46

Randor

15-Dec-11 5:46

Hi Gopal,

Member 8488014 wrote:
My WinForm application uses C++ runtime dll's(msvcm80.dll, msvcp80.dll and msvcr80.dll) and bundling them as part of the application. How to make sure that my application will use the C++ runtime dll's that bundled along with product even though the dll's present else where in the system(c:\Windows\Winsxs)

Based on your description it seems that perhaps you want to 'Bind to a specific MFC runtime'. If I am correct then you should have a look at #defining:

C++

#define _BIND_TO_CURRENT_MFC_VERSION 1

Some documentation on MSDN that covers this subject:

Redistributing an Application and Binding It to Specific Libraries[^]

Best Wishes,
-David Delaune

Re: Use the environment provided by the application instead from system environment.

Member 848801418-Dec-11 21:25

Member 8488014

18-Dec-11 21:25

Thanks for the reference.

We are using Visual Studio 2005 as development environment.
I've not seen any option BIND_TO_CURRENT_VCLIBS_VERSION=1 on the C/C Preprocessor Definitions configuration page.
The article also states, it is only applicable of VS2008.

Re: Use the environment provided by the application instead from system environment.

Randor 19-Dec-11 6:38

Randor

19-Dec-11 6:38

Hi Gopal,

Yep, you are correct and BIND_TO_CURRENT_VCLIBS_VERSION will only work for VS2008 and above. It is defined in the crtassem.h file.

However... if you take a closer look... you will find that by defining BIND_TO_CURRENT_VCLIBS_VERSION ... all it does it change the manifest.

I would suggest that you read the article by Martin Richter:

Create projects easily with private MFC, ATL and CRT assemblies[^]

Perhaps a private assembly would allow you to use a local copy of the MFC/CRT runtime.

Best Wishes,
-David Delaune

TAPI Call program

Hadi Dayvary14-Dec-11 4:52

Hadi Dayvary

14-Dec-11 4:52

Hi
I have writen a TAPI program that can call (works fine)

I want to speak via headset not picking up a phone.
I can do this with Venta Fax & Voice program in my PC (so the modem supports this), but my program can not do this (no sounds send/receive).

Is there any tricks in TAPI function for this?

I have used

C++

LINEMEDIAMODE_AUTOMATEDVOICE

for

C++

lineOpen

function like this:

C++

lineOpen(m_hLineApp, m_nDevID, &m_hLine, dwTAPIVer, 0, 1, LINECALLPRIVILEGE_MONITOR | LINECALLPRIVILEGE_OWNER, LINEMEDIAMODE_AUTOMATEDVOICE, NULL);

Regards

www.logicsims.ir

Re: TAPI Call program

rahul.kulshreshtha15-Dec-11 19:24

rahul.kulshreshtha

15-Dec-11 19:24

I think you need to take the handle of your headphone. There are 4 or 5 defined steps (function calling) which you should do for establishing a proper communication channel.

See this link.
http://www.tapi.info/default.aspx/TAPI/PSDKSamples.html[^]

Most of these samples are working perfectly however some may not work. Also make sure you are having bi-direction modem otherwise only one side sound will come.

Enjoy TAPI !!!

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