CryptProtectData output to a file
Date: 05/13/05

Date: 13 May 2005 09:32:41 -0700

Hi. I am using the DPAPI and the CryptProtectData method to encrypt a
database password. I need to be able to access my program that
encrypts and decrypts the password from TCL and PHP, so I would like to
write a command line program that accepts a cleartext password and
returns the encrypted string. I'll also have to accept the encrypted
string and return the cleartext password.

The problem that I am having is that I can't figure out how to output
DATA_BLOB in such a way that I can store it and then re submit it back
to de-crypt it. I tried writing it to a text file and then reading in
the text file, but that doesn't work.

Any thoughts would be helpful.

I've included my sample prototype below, if that helps. (I'm working
from the MSDN example)



#include <stdio.h>
#include <windows.h>
#include <wincrypt.h>
#include <iostream>
#include <fstream>
using namespace std;
void MyHandleError(char *s);

void main()

// Copyright (c) Microsoft Corporation. All rights reserved.
// Encrypt data from DATA_BLOB DataIn to DATA_BLOB DataOut.
// Then decrypt to DATA_BLOB DataVerify.

// Declare and initialize variables.

DATA_BLOB DataVerify;
BYTE *pbDataInput =(BYTE *)"Hello world of data protection.";
DWORD cbDataInput = strlen((char *)pbDataInput)+1;
DataIn.pbData = pbDataInput;
DataIn.cbData = cbDataInput;
LPWSTR pDescrOut = NULL;

// Begin processing.

printf("The data to be encrypted is: %s\n",pbDataInput);

// Begin protect phase.

     L"This is the description string.", // A description string.
     NULL, // Optional entropy
                                             // not used.
     NULL, // Reserved.
     NULL, // Pass a PromptStruct.
     printf("The encryption phase worked. \n");

         ofstream myOutputFile ("output.txt", ios::out);

         for (unsigned int i=0;i<DataOut.cbData;i++){


        printf( "\n");
    MyHandleError("Encryption error!");
// Begin unprotect phase.
BYTE buffer[10000];
memset (buffer, 0,10000);
         int i=0;
 ifstream myInputFile ("output.txt", ios::in);
 while (myInputFile >> buffer){i++;};

DWORD cbDataOutput = DataOut.cbData;
DataOut.pbData = (BYTE*)&buffer;
DataOut.cbData = DataIn.cbData;

if (CryptUnprotectData(
        NULL, // Optional entropy
        NULL, // Reserved
        NULL, // Optional PromptStruct
     printf("The decrypted data is: %s\n", DataVerify.pbData);
     printf("The description of the data was: %S\n",pDescrOut);
    MyHandleError("Decryption error!");
// At this point, memcmp could be used to compare DataIn.pbData and
// DataVerify.pbDate for equality. If the two functions worked
// correctly, the two byte strings are identical.

// Clean up.

} // End of main

// This example uses the function MyHandleError, a simple error
// handling function, to print an error message to the
// standard error (stderr) file and exit the program.
// For most applications, replace this function with one
// that does more extensive error reporting.

void MyHandleError(char *s)
    fprintf(stderr,"An error occurred in running the program. \n");
    fprintf(stderr, "Error number %x.\n", GetLastError());
    fprintf(stderr, "Program terminating. \n");
} // End of MyHandleError

Relevant Pages

  • RE: 2007 User Level Security
    ... encrypted string. ... the way I use it is to encrypt user names and passwords and store the ... Dim prp As Property ... Dim dbs As Object, prp As Variant ...
  • Re: Workable encryption in Tcl??
    ... The longest string would be about the length ... How to encrypt a string ... nothing about binary formats. ... ># Perform ECB mode encryption on a plaintext block of BINARY data. ...
  • RE: Using Win32 CryptDecrypt to Decrypt RijndaelManaged
    ... I figured out how to use RijndaelManaged with AES in the C++ app. ... C++ crypto WILL successfully decrypt the .NET generated ... I am trying to write a Win32 app that can decrypt that string using the ... I can get both to encrypt and decrypt successfully in their own projects, ...
  • Re: Decryptionfailed to bring original text back....
    ... cryptography, but now using them on web.config, any idea, I like to ... There isn't really much reason to encrypt a .NET string with ... what happen when you decrypt the encrypted ...
  • Re: Decryptionfailed to bring original text back....
    ... them when it is not being used, decrypt them when connecting to database. ... arbitrary binary data) is that if you have a .NET string object, ... There isn't really much reason to encrypt a .NET string with ... I just started learning cryptography. ...