Re: Encryption/Decryption - C / C++ / MFC Discussion Boards

Sorry, i had not thought that you could have used the value associated to your button (i prefer using controls). Riazi got me on this one. Poke tongue | ;-P

~RaGE();

Hi all,
I want to delete the history, cache entries and cookies craeted by internet thru programming..Is there any good tutorial or can anyone guide me so as how to do it...Any thoughts and ideas are most welcome..
Thanks in advance..

Himanshu

Just call some shell function to retrieve folders of Temprory Internet Files and also History then delete all of files on it!
For more information on how to retrieve shell folders path, view my article: System Information[^].
A. Riazi

Take a look at this article:

http://www.codeproject.com/shell/surfhelper.asp[^]

Regards,

Rohit Sinha

thanks buddy..this was what I was looking for....thans a lot..
cheers

Himanshu

i am using CALG_MD5 to encrypt/decrypt a string. it encryts the text but in decrypting it shows error "NTE_BAD_DATA" on lastblock other blocks are decrypted well. How can i resolve this erro.
Note:
final parameter is set to true for last block.

Zaid Ansari wrote:
am using CALG_MD5 to encrypt/decrypt a string

Are you sure you are using MD5 for encyrption/decryption? MD5 is an hash-algorithm so its result can't be "decrypted". Search the net for information about hashing vs. encrypting/decrypting. You could use algorithms like AES or DES for your needs.

--

karl

thanks karl,
i know that MD5 is a one way hash but i dont have any experiance in VC can u please tell me if i am making any mistake in this code.

to //code
if(!CryptAcquireContext(&hCryptProv, NULL, NULL, PROV_RSA_FULL,0))
{
}
// Create a hash object.
if(!CryptCreateHash(hCryptProv, CALG_MD5, 0, 0, &hHash))
{
strcat(strErrorMessage, "Error executing CryptCreateHash");
return NULL;
}

if(!CryptHashData(hHash, (BYTE *)password, strlen(password), 0))
{
strcat(strErrorMessage, "Error executing CryptHashData");
return NULL;
}
// Derive a session key from the hash object.
if(!CryptDeriveKey(hCryptProv, CONST_ENCRYPT_ALGORITHM, hHash, 0, &hKey))
{
strcat(strErrorMessage, "Error executing CryptDeriveKey");
return NULL;
}

// Destroy the hash object.
CryptDestroyHash(hHash);
hHash = 0;

// Determine number of bytes to encrypt at a time.
// This must be a multiple of CONST_ENCRYPT_BLOCK_SIZE.
// CONST_ENCRYPT_BLOCK_SIZE is set by a #define statement.
dwBlockLen = 10 - 10 % CONST_ENCRYPT_BLOCK_SIZE;
// get data block as close to 1000 bytes as possible making sure it's a multiple of ENCRYPT_BLOCK_SIZE

// Determine the block size. If a block cipher is used,
// it must have room for an extra block.
if(CONST_ENCRYPT_BLOCK_SIZE > 1)
dwBufferLen = dwBlockLen + CONST_ENCRYPT_BLOCK_SIZE;
else
dwBufferLen = dwBlockLen;

// Allocate memory.
pbBuffer = (BYTE *)malloc(dwBufferLen);
BYTE *pAllBlocks = NULL;
BYTE *pPreviousBlocks = NULL;
bool fMoreDataExists = true;
DWORD dwIndex = 0;
DWORD dwLength;
DWORD dwLengthOfEncryptedData;
DWORD dwAllBlocksLength, dwPreviousBlocksLength;

// Make way through data one block at a time. Find out how big
// each encrypted string will be, allocate memory for it, and save
// in array.
do
{
// get next block of clear text data
GetBYTEDataBlockFromString(dwIndex, pClearTextString, dwBlockLen, pbBuffer, dwLength);
// check if more data exists after current block

if (dwIndex >= strlen(pClearTextString))
fMoreDataExists = false;

// encrypt current data block
dwLengthOfEncryptedData = dwLength;
if(!CryptEncrypt(hKey, 0, !fMoreDataExists, 0, pbBuffer, &dwLengthOfEncryptedData, dwBufferLen))
{
fout<<"Error Occured in CryptEncrypt";
}
if (pAllBlocks)
delete [] pAllBlocks;
if (pPreviousBlocks)
dwAllBlocksLength = dwPreviousBlocksLength + dwLengthOfEncryptedData;
else
dwAllBlocksLength = dwLengthOfEncryptedData;

pAllBlocks = new BYTE[dwAllBlocksLength];
if (!pAllBlocks)
{
if(pbBuffer)
free(pbBuffer);
if (pPreviousBlocks)
delete [] pPreviousBlocks;
strcat(strErrorMessage, "Unable to allocate memory for pAllBlocks");
FreeAllCryptHandles(hKey, hHash, hCryptProv);
return NULL;
}
// copy all encrypted data to pAllBlocks

if (pPreviousBlocks)
{
CopyBYTEData(dwPreviousBlocksLength, pPreviousBlocks, pAllBlocks, dwAllBlocksLength, 0);
CopyBYTEData(dwLengthOfEncryptedData, pbBuffer, pAllBlocks, dwAllBlocksLength, dwPreviousBlocksLength);
delete [] pPreviousBlocks;
}
else
CopyBYTEData(dwLengthOfEncryptedData, pbBuffer, pAllBlocks, dwAllBlocksLength, 0);

if (fMoreDataExists)
{ // save previous data blocks for next iteration of this do loop
dwPreviousBlocksLength = dwAllBlocksLength;
pPreviousBlocks = new BYTE[dwPreviousBlocksLength];
if (!pPreviousBlocks)
{
if(pbBuffer)
free(pbBuffer);
if (pAllBlocks)
delete [] pAllBlocks;
strcat(strErrorMessage, "Unable to allocate memory for pPreviousBlocks");
FreeAllCryptHandles(hKey, hHash, hCryptProv);
return NULL;
}
else
CopyBYTEData(dwAllBlocksLength, pAllBlocks, pPreviousBlocks, dwPreviousBlocksLength, 0);
}
}
while(fMoreDataExists);

can any one send me code for encryption/decryption string using DES.

It's not DES, but it uses the Windows-CryptAPI.
On the other hand I'm quite sure there is a class outside in the wild which provides DES-encryption.

	<br />
HCRYPTPROV hCryptProv;<br />
HCRYPTKEY hKey;<br />
HCRYPTHASH hHash;<br />
<br />
if ( !CryptAcquireContext(&hCryptProv, NULL , NULL, PROV_RSA_FULL,  0))<br />
    AfxMessageBox("Error Acquire");<br />
<br />
if ( !CryptCreateHash(hCryptProv, CALG_MD5, 0, 0, &hHash))<br />
    AfxMessageBox("Error CreateHash");<br />
<br />
if ( !CryptHashData(hHash, (BYTE*) "YourKey", (DWORD)strlen("YourKey"), 0))<br />
    AfxMessageBox("Error Hashing");<br />
<br />
if ( !CryptDeriveKey(hCryptProv, CALG_RC4, hHash, 0, &hKey))<br />
    AfxMessageBox("Error Derive Key");<br />
<br />
BYTE* buf; //The thing you want to encrypt<br />
DWORD size = (DWORD)strlen((char*)buf);<br />
     <br />
CryptEncrypt(hKey, NULL, TRUE, 0, (BYTE*)buf, &size, size);<br />
<br />
CryptDecrypt(hKey, NULL, TRUE, 0, (BYTE*)buf, &size)<br />
<br />

This works fine for me. It's not a high-security app, so i hardcoded the encryption-key in the code. I simply took the Class-Name as key.

Hope I could help.

--

karl

i need simple DES encryption / decryption with hardcoded key. Thanks a lot Karl i will try this.

Thanks a lot Mr.Karl, it worked but now i have data which contanis 300 character but it encrypts forst 56 characters only. can u please tell me how can i do this both encryption and decryption.

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/security/Security/cryptencrypt.asp

--

karl

thanks karl,
i have 2 questions.
1. i implemented that code it encrypts first 56 characters 8 in each cryptencrypt call on next call it founds "space character" as first character in block it can not encrypt it,next blocks are encrypted but not added to result just because of "Space character".
How can i resolve this problem.

and my next question is that i am writing this code to be a platform independent can i implement same encryption/decryption in jave,
i will encrypt text in VC and Decrypt it in Java and vice versa.

can u please send me some sample code for block cipher and stream cipher.

if i nned to use some other algorithm than can u please send some sample.
Zaid

If I have a double type field in a jet database and the value 8.95 stored in it then when I retrieve it from the database as a string representaion it gives me "8.9499999999999993"

Is this just because the double type cannot represent the value 8.95 exactly? I have noticed that not all values come back as a huge string, e.g. 10.99, 1.95, and 8.5 are all exactly as entered. Or is it a bug with the code in the database driver that is doing the conversion?

Binary representations of floating point numbers are pretty interesting. If you read the link below, you can see that IEEE floating point numbers can't represent 1/10 exactly, which you would think is strange, but since it's represented in binary, isn't so strange. Anyways, I don't have the answer to your question, but I bet somewhere in the MSDN does (maybe even the link below?).

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore/html/_core_IEEE_Floating.2d.Point_Representation_and_Microsoft_Languages.asp[^]

Chris Richardson

Programmers find all sorts of ingenious ways to screw ourselves over. - Tim Smith

Does anyone know the technique to allow a background bitmap to be displayed for a CProgessCtrl.

Specifically what functions to override and implement. I think it is not possible to use DrawItem unless you make CProgressCtrl to be Owner Drawn.

Many Thanks In Advance

Hi,
I dont know can implement this technique or not? But this is an idea:
1- Create a PictureBox control to show your bitmap
2- Use SetParent API function to change parent of PictureBox control.
3- Set your ProgressBar control as parent of bitmap PictureBox.

A. Riazi

i have KaZZA and i was wondering if it's legal if i download a version of Visual C++ 6.0, if i did would i be able to register it without WINDOWS coming and knocking on my door telling me to give it up, lol

Behold, this years winner in the 'stupidest man of the year contest'.

Yeah, it's legal, just send your details to piracy@microsoft.com and they will fix you up.

Christian

No offense, but I don't really want to encourage the creation of another VB developer.
- Larry Antram 22 Oct 2002

C# will attract all comers, where VB is for IT Journalists and managers - Michael
P Butler 05-12-2002

It'd probably be fairly easy to make a bot that'd post random stupid VB questions, and nobody would probably ever notice - benjymous - 21-Jan-2003

I am attempting to programmatically create a copy of a shortcut using the IShelllink interface. When I interogate most *.lnk files, the GetPath function returns a true target ie. "C:\Program Files\Adobe\Acrobat 5.0\Reader\AcroRd32.exe". There are some special shortcuts however, that behave differently. For example, a shortcut to MS Word returns the
C:\windows\installer\{ some guid }\wordicon.exe. from the GetPath function.

How can I determine the true target (ie: winword.exe ) given the information from the IShelllink functions?

Any suggestions?

from http://www.codeproject.com/editctrl/dropedit.asp[^]

CString ExpandShortcut(CString &inFile)
{
	CString outFile = "";
	
    // Make sure we have a path
    ASSERT(inFile != _T(""));
	
    IShellLink* psl;
    HRESULT hres;
    LPTSTR lpsz = inFile.GetBuffer(MAX_PATH);
	
    // Create instance for shell link
    hres = ::CoCreateInstance(CLSID_ShellLink, NULL, CLSCTX_INPROC_SERVER,
        IID_IShellLink, (LPVOID*) &psl);
    if (SUCCEEDED(hres))
    {
        // Get a pointer to the persist file interface
        IPersistFile* ppf;
        hres = psl->QueryInterface(IID_IPersistFile, (LPVOID*) &ppf);
        if (SUCCEEDED(hres))
        {
            // Make sure it's ANSI
            WORD wsz[MAX_PATH];
            ::MultiByteToWideChar(CP_ACP, 0, lpsz, -1, wsz, MAX_PATH);
			
            // Load shortcut
            hres = ppf->Load(wsz, STGM_READ);
            if (SUCCEEDED(hres)) {
				WIN32_FIND_DATA wfd;
				// find the path from that
				HRESULT hres = psl->GetPath(outFile.GetBuffer(MAX_PATH), 
					MAX_PATH,
					&wfd, 
					SLGP_UNCPRIORITY);
				
				outFile.ReleaseBuffer();
            }
            ppf->Release();
        }
        psl->Release();
    }
	
	inFile.ReleaseBuffer();
	
	// if this fails, outFile == ""
    return outFile;
}

A | B - it's not a choice.

ThumbNailer

We actually do just what is described above. We are interogating the Microsoft Word.lnk file ( the shortcut installed in the Documents and Settings\AllUsers.Windows\StartMenu\Programs\Office\Microsoft Word.lnk). The problem is, the IShellLink->GetPath function returns C:\windows\installer\{ GUID }\wordicon.exe . But we all know that when a user runs Microsoft Word, the process running is called winword.exe. How does the system launch winword.exe when the shortcut target is wordicon.exe ? Smile | :)

We actually do just what is described above. We are interogating the Microsoft Word.lnk file ( the shortcut installed in the Documents and Settings\AllUsers.Windows\StartMenu\Programs\Office\Microsoft Word.lnk). The problem is, the IShellLink->GetPath function returns C:\windows\installer\{ GUID }\wordicon.exe . But we all know that when a user runs Microsoft Word, the process running is called winword.exe. How does the system launch winword.exe when the shortcut target is wordicon.exe ? Smile | :)

hi,

how do you make the header, in report mode(list control), not clickable?

thx in advance!