Försöker följa guiden på denna adress:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnnetsec/html/secnetlpMSDN.asp
När jag kör "Build Solution" kompileras dllén OK.
Men när jag anropar dllén, med kod på denna länk:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnnetsec/html/secnetlpMSDN.asp
Får jag detta fel när jag vill dekryptera:Decryption Failed. Felaktig data.
Att kryptera går bra utan felmeddelande.
Ifall någon finner detta intressant vore jag tacksam för hjälp.
Bifogar den kod jag lyckas knåpa ihop efter guiden "Create DPAPI..." jag är inte säker att jag får till den rätt.

using System;
using System.Text;
using System.Runtime.InteropServices;


namespace DataProtection
{
/// <summary>
/// Summary description for Class1.
/// </summary>
public class DataProtector
{

[DllImport("Crypt32.dll", SetLastError=true,
CharSet=System.Runtime.InteropServices.CharSet.Auto)]
private static extern bool CryptProtectData(
ref DATA_BLOB pDataIn,
String szDataDescr,
ref DATA_BLOB pOptionalEntropy,
IntPtr pvReserved,
ref CRYPTPROTECT_PROMPTSTRUCT
pPromptStruct,
int dwFlags,
ref DATA_BLOB pDataOut);
[DllImport("Crypt32.dll", SetLastError=true,
CharSet=System.Runtime.InteropServices.CharSet.Auto)]
private static extern bool CryptUnprotectData(
ref DATA_BLOB pDataIn,
String szDataDescr,
ref DATA_BLOB pOptionalEntropy,
IntPtr pvReserved,
ref CRYPTPROTECT_PROMPTSTRUCT
pPromptStruct,
int dwFlags,
ref DATA_BLOB pDataOut);
[DllImport("kernel32.dll",
CharSet=System.Runtime.InteropServices.CharSet.Auto)]
private unsafe static extern int FormatMessage(int dwFlags,
ref IntPtr lpSource,
int dwMessageId,
int dwLanguageId,
ref String lpBuffer,
int nSize,
IntPtr *Arguments);



[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Unicode)]
internal struct DATA_BLOB
{
public int cbData;
public IntPtr pbData;
}

[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Unicode)]
internal struct CRYPTPROTECT_PROMPTSTRUCT
{
public int cbSize;
public int dwPromptFlags;
public IntPtr hwndApp;
public String szPrompt;
}
static private IntPtr NullPtr = ((IntPtr)((int)(0)));
private const int CRYPTPROTECT_UI_FORBIDDEN = 0x1;
private const int CRYPTPROTECT_LOCAL_MACHINE = 0x4;


public enum Store {USE_MACHINE_STORE = 1, USE_USER_STORE};
private Store store;
public DataProtector(Store tempStore)
{
store = tempStore;
}





public byte[] Decrypt(byte[] cipherText, byte[] optionalEntropy)
{
bool retVal = false;
DATA_BLOB plainTextBlob = new DATA_BLOB();
DATA_BLOB cipherBlob = new DATA_BLOB();
CRYPTPROTECT_PROMPTSTRUCT prompt = new
CRYPTPROTECT_PROMPTSTRUCT();
InitPromptstruct(ref prompt);
try
{
try
{
int cipherTextSize = cipherText.Length;
cipherBlob.pbData = Marshal.AllocHGlobal(cipherTextSize);
if(IntPtr.Zero == cipherBlob.pbData)
{
throw new Exception("Unable to allocate cipherText buffer.");
}
cipherBlob.cbData = cipherTextSize;
Marshal.Copy(cipherText, 0, cipherBlob.pbData,
cipherBlob.cbData);
}
catch(Exception ex)
{
throw new Exception("Exception marshalling data. " +
ex.Message);
}
DATA_BLOB entropyBlob = new DATA_BLOB();
int dwFlags;
if(Store.USE_MACHINE_STORE == store)
{//Using the machine store, should be providing entropy.
dwFlags =
CRYPTPROTECT_LOCAL_MACHINE|CRYPTPROTECT_UI_FORBIDDEN;
//Check to see if the entropy is null
if(null == optionalEntropy)
{//Allocate something
optionalEntropy = new byte[0];
}
try
{
int bytesSize = optionalEntropy.Length;
entropyBlob.pbData = Marshal.AllocHGlobal(bytesSize);
if(IntPtr.Zero == entropyBlob.pbData)
{
throw new Exception("Unable to allocate entropy buffer.");
}
entropyBlob.cbData = bytesSize;
Marshal.Copy(optionalEntropy, 0, entropyBlob.pbData,
bytesSize);
}
catch(Exception ex)
{
throw new Exception("Exception entropy marshalling data. " +
ex.Message);
}
}
else
{//Using the user store
dwFlags = CRYPTPROTECT_UI_FORBIDDEN;
}
retVal = CryptUnprotectData(ref cipherBlob, null, ref
entropyBlob,
IntPtr.Zero, ref prompt, dwFlags,
ref plainTextBlob);
if(false == retVal)
{
throw new Exception("Decryption failed. " +
GetErrorMessage(Marshal.GetLastWin32Error()));
}
//Free the blob and entropy.
if(IntPtr.Zero != cipherBlob.pbData)
{
Marshal.FreeHGlobal(cipherBlob.pbData);
}
if(IntPtr.Zero != entropyBlob.pbData)
{
Marshal.FreeHGlobal(entropyBlob.pbData);
}
}
catch(Exception ex)
{
throw new Exception("Exception decrypting. " + ex.Message);
}
byte[] plainText = new byte[plainTextBlob.cbData];
Marshal.Copy(plainTextBlob.pbData, plainText, 0,
plainTextBlob.cbData);
return plainText;
}




private void InitPromptstruct(ref CRYPTPROTECT_PROMPTSTRUCT ps)
{
ps.cbSize = Marshal.SizeOf(typeof(CRYPTPROTECT_PROMPTSTRUCT));
ps.dwPromptFlags = 0;
ps.hwndApp = NullPtr;
ps.szPrompt = null;
}

private unsafe static String GetErrorMessage(int errorCode)
{
int FORMAT_MESSAGE_ALLOCATE_BUFFER = 0x00000100;
int FORMAT_MESSAGE_IGNORE_INSERTS = 0x00000200;
int FORMAT_MESSAGE_FROM_SYSTEM = 0x00001000;
int messageSize = 255;
String lpMsgBuf = "";
int dwFlags = FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM |
FORMAT_MESSAGE_IGNORE_INSERTS;
IntPtr ptrlpSource = new IntPtr();
IntPtr prtArguments = new IntPtr();
int retVal = FormatMessage(dwFlags, ref ptrlpSource, errorCode, 0,
ref lpMsgBuf, messageSize,
&prtArguments);
if(0 == retVal)
{
throw new Exception("Failed to format message for error code " +
errorCode + ". ");
}
return lpMsgBuf;
}




public byte[] Encrypt(byte[] plainText, byte[] optionalEntropy)
{
bool retVal = false;

DATA_BLOB plainTextBlob = new DATA_BLOB();
DATA_BLOB cipherTextBlob = new DATA_BLOB();
DATA_BLOB entropyBlob = new DATA_BLOB();

CRYPTPROTECT_PROMPTSTRUCT prompt = new
CRYPTPROTECT_PROMPTSTRUCT();
InitPromptstruct(ref prompt);

int dwFlags;
try
{
try
{
int bytesSize = plainText.Length;
plainTextBlob.pbData = Marshal.AllocHGlobal(bytesSize);
if(IntPtr.Zero == plainTextBlob.pbData)
{
throw new Exception("Unable to allocate plaintext buffer.");
}
plainTextBlob.cbData = bytesSize;
Marshal.Copy(plainText, 0, plainTextBlob.pbData, bytesSize);
}
catch(Exception ex)
{
throw new Exception("Exception marshalling data. " +
ex.Message);
}
if(Store.USE_MACHINE_STORE == store)
{//Using the machine store, should be providing entropy.
dwFlags =
CRYPTPROTECT_LOCAL_MACHINE|CRYPTPROTECT_UI_FORBIDDEN;
//Check to see if the entropy is null
if(null == optionalEntropy)
{//Allocate something
optionalEntropy = new byte[0];
}
try
{
int bytesSize = optionalEntropy.Length;
entropyBlob.pbData =
Marshal.AllocHGlobal(optionalEntropy.Length);;
if(IntPtr.Zero == entropyBlob.pbData)
{
throw new Exception("Unable to allocate entropy data buffer.");
}
Marshal.Copy(optionalEntropy, 0, entropyBlob.pbData,
bytesSize);
entropyBlob.cbData = bytesSize;
}
catch(Exception ex)
{
throw new Exception("Exception entropy marshalling data. " +
ex.Message);
}
}
else
{//Using the user store
dwFlags = CRYPTPROTECT_UI_FORBIDDEN;
}
retVal = CryptProtectData(ref plainTextBlob, "", ref
entropyBlob,
IntPtr.Zero, ref prompt, dwFlags,
ref cipherTextBlob);
if(false == retVal)
{
throw new Exception("Encryption failed. " +
GetErrorMessage(Marshal.GetLastWin32Error()));
}
//Free the blob and entropy.
if(IntPtr.Zero != cipherTextBlob.pbData)
{
Marshal.FreeHGlobal(cipherTextBlob.pbData);
}
if(IntPtr.Zero != entropyBlob.pbData)
{
Marshal.FreeHGlobal(entropyBlob.pbData);
}
}
catch(Exception ex)
{
throw new Exception("Exception encrypting. " + ex.Message);
}
byte[] cipherText = new byte[cipherTextBlob.cbData];
Marshal.Copy(cipherTextBlob.pbData, cipherText, 0,
cipherTextBlob.cbData);
return cipherText;
}




public DataProtector()
{
//
// TODO: Add constructor logic here
//



}
}
}