CryptGenKey: Unterschied zwischen den Versionen

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                 ByRef phKey As Long) As Long</vb>
 
                 ByRef phKey As Long) As Long</vb>
  
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+
===Parameter===
 +
''phProv''
 +
:[in] Handle zu einem CSP. Ein solches Handle wird mit [[CryptAcquireContext]] erzeugt.
 +
 
 +
''AlgID''
 +
:[in] Definiert den Verschlüsselungsalgorithmus für den der Schlüssel verwendet wird. Beispiele sind: [[CryptGenKeyAlgID|CALG_AES_128]] oder [[CryptGenKeyAlgID|CALG_3DES_112]]
 +
 
 +
''dwFlags''
 +
:[in] Flags welche die Schlüsselerstellung weiter steuern, z.B. [[CryptGenKeyFlags|CRYPT_EXPORTABLE]]. Mittels der oberen 16 Bits kann ausserdem die gewünschte Schlüssellänge angegeben werden.
 +
 
 +
''phKey''
 +
:[out] In diesem Long Wert wird das Handle des erstellten Schlüssels zurückgegeben. Um den Schlüssel zu zerstören wird [[CryptDestroyKey]] verwendet.
  
 
===Rückgabe(n)===
 
===Rückgabe(n)===

Version vom 3. Oktober 2011, 10:30 Uhr

Die Funktion CryptGenKey erstellt einen zufälligen Schlüssel zur Verschlüsselung von Daten.

<vb> Declare Function CryptGenKey Lib "advapi32.dll" ( _

                ByVal hProv As Long, _
                ByVal AlgID As Long, _
                ByVal dwFlags As Long, _
                ByRef phKey As Long) As Long</vb>

Parameter

phProv

[in] Handle zu einem CSP. Ein solches Handle wird mit CryptAcquireContext erzeugt.

AlgID

[in] Definiert den Verschlüsselungsalgorithmus für den der Schlüssel verwendet wird. Beispiele sind: CALG_AES_128 oder CALG_3DES_112

dwFlags

[in] Flags welche die Schlüsselerstellung weiter steuern, z.B. CRYPT_EXPORTABLE. Mittels der oberen 16 Bits kann ausserdem die gewünschte Schlüssellänge angegeben werden.

phKey

[out] In diesem Long Wert wird das Handle des erstellten Schlüssels zurückgegeben. Um den Schlüssel zu zerstören wird CryptDestroyKey verwendet.

Rückgabe(n)

Bei Erfolg wird ein Wert ungleich 0 zurückgegeben.

Beispiel

<vb>Const CALG_RSA_SIGN As Long = (ALG_CLASS_SIGNATURE Or ALG_TYPE_RSA Or ALG_SID_RSA_ANY)

   If CryptGenKey(hCryptProv, CALG_RSA_SIGN, KeyLength * &H10000 Or _
           CRYPT_EXPORTABLE, hRsaKey) = 0 Then
       Err.Raise Err.LastDllError, , "CryptGenKey Error!"
   End If</vb>

Ein komplettes Beispiel zum Ver- und Entschlüsseln findet sich unter CryptDecrypt

Das folgende Beispiel zeigt den sicheren Austausch eines (symmetrischen) DES Schlüssels mit Hilfe des asymmetrischen RSA Algorithmus: <vb> Option Explicit

Private Declare Function CryptAcquireContext Lib "advapi32.dll" _

                Alias "CryptAcquireContextA" ( _
                ByRef phProv As Long, _
                ByVal pszContainer As String, _
                ByVal pszProvider As String, _
                ByVal dwProvType As Long, _
                ByVal dwFlags As Long) As Long

Private Declare Function CryptReleaseContext Lib "advapi32.dll" ( _

                ByVal hProv As Long, _
                ByVal dwFlags As Long) As Long

Private Declare Function CryptDestroyKey Lib "advapi32.dll" ( _

                ByVal hKey As Long) As Long

Private Declare Function CryptGenKey Lib "advapi32.dll" ( _

                ByVal hProv As Long, _
                ByVal AlgID As Long, _
                ByVal dwFlags As Long, _
                ByRef phKey As Long) As Long

Private Declare Function CryptGetUserKey Lib "advapi32.dll" ( _

                ByVal hProv As Long, _
                ByVal dwKeySpec As Long, _
                ByRef phUserKey As Long) As Long

Private Declare Function CryptExportKey Lib "advapi32.dll" ( _

                ByVal hKey As Long, _
                ByVal hExhKey As Long, _
                ByVal dwBlobType As Long, _
                ByVal dwFlags As Long, _
                ByRef pbData As Any, _
                ByRef pdwDataLen As Long) As Long

Private Declare Function CryptImportKey Lib "advapi32.dll" ( _

                ByVal hProv As Long, _
                ByRef pbData As Any, _
                ByVal dwDataLen As Long, _
                ByVal hPubKey As Long, _
                ByVal dwFlags As Long, _
                ByRef phKey As Long) As Long

Private Declare Function CryptEncrypt Lib "advapi32.dll" ( _

                ByVal hKey As Long, _
                ByVal hHash As Long, _
                ByVal Final As Long, _
                ByVal dwFlags As Long, _
                ByVal pbData As Long, _
                ByRef pdwDataLen As Long, _
                ByVal dwBufLen As Long) As Long

Private Declare Function CryptDecrypt Lib "advapi32.dll" ( _

                ByVal hKey As Long, _
                ByVal hHash As Long, _
                ByVal Final As Long, _
                ByVal dwFlags As Long, _
                ByVal pbData As Long, _
                ByRef pdwDataLen As Long) As Long


Private Const MS_DEF_PROV As String = _

                   "Microsoft Base Cryptographic Provider v1.0"

Private Const PROV_RSA_FULL As Long = 1

Private Const CRYPT_NEWKEYSET As Long = &H8

Private Const CRYPT_EXPORTABLE As Long = &H1

Private Const CRYPT_NO_SALT As Long = &H10

Private Const CRYPT_DELETEKEYSET As Long = &H10

Private Const AT_KEYEXCHANGE As Long = 1

Private Const PUBLICKEYBLOB As Long = &H6

Private Const SIMPLEBLOB As Long = &H1

Const ALG_CLASS_KEY_EXCHANGE As Long = &HA000& Const ALG_CLASS_HASH As Long = &H8000& Const ALG_CLASS_DATA_ENCRYPT As Long = &H6000& Const ALG_CLASS_SIGNATURE As Long = &H2000& Const ALG_TYPE_STREAM As Long = &H800& Const ALG_TYPE_BLOCK As Long = &H600& Const ALG_TYPE_RSA As Long = &H400& Const ALG_TYPE_ANY As Long = 0 Const ALG_SID_RSA_ANY As Long = 0 Const ALG_SID_MD2 As Long = 1 Const ALG_SID_MD4 As Long = 2 Const ALG_SID_MD5 As Long = 3 Const ALG_SID_SHA As Long = 4 Const ALG_SID_SHA_256 As Long = 12 Const ALG_SID_SHA_384 As Long = 13 Const ALG_SID_SHA_512 As Long = 14 Const ALG_SID_RC4 As Long = 1 Const ALG_SID_DES As Long = 1 Const ALG_SID_RC2 As Long = 2 Const ALG_SID_3DES As Long = 3 Const ALG_SID_3DES_112 As Long = 9 Const ALG_SID_AES_128 As Long = 14 Const ALG_SID_AES_192 As Long = 15 Const ALG_SID_AES_256 As Long = 16 Const ALG_SID_AES As Long = 17

'Encryption: Public Enum EnmCryptAlgo

   CALG_RC2 = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_RC2)
   CALG_RC4 = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_STREAM Or ALG_SID_RC4)
   CALG_DES = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_DES)
   CALG_3DES = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_3DES)
   CALG_3DES_112 = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_3DES_112)
   CALG_AES_128 = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_AES_128)
   CALG_AES_192 = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_AES_192)
   CALG_AES_256 = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_AES_256)

End Enum

'Rsa Keyexchange and Signature Algorithmen (asymmetrisch): Enum EnmRsaKeyTypes

   CALG_RSA_SIGN = (ALG_CLASS_SIGNATURE Or ALG_TYPE_RSA Or ALG_SID_RSA_ANY)
   CALG_RSA_KEYX = (ALG_CLASS_KEY_EXCHANGE Or ALG_TYPE_RSA Or ALG_SID_RSA_ANY)

End Enum

Private Sub Command1_Click()

   Dim hCryptProvA As Long
   Dim hPrivateKey As Long
   Dim hSessionKeyA As Long
   
   Dim hCryptProvB As Long
   Dim hPublicKey As Long
   Dim hSessionKeyB As Long
   
   Dim cbData As Long
   Dim btPublicKey() As Byte
   Dim btSessionKeyData() As Byte
   Dim btData() As Byte
   Dim x As Long
   
   '<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
   'Partner A erstellt einen RSA KeyExchange Schlüssel und exportiert den öffentlichen
   'Schlüsselteil:
   '--------------------------------------------------------------------------------------
   'Provider Kontext anfordern und gegebenenfalls RSA KeyExchange Schlüssel erstellen:
   If CryptAcquireContext(hCryptProvA, "Mein Container A", MS_DEF_PROV, PROV_RSA_FULL, CRYPT_NEWKEYSET) = 0 Then
       'Fehler->Existiert der Container bereits?
       If CryptAcquireContext(hCryptProvA, "Mein Container A", MS_DEF_PROV, PROV_RSA_FULL, 0) = 0 Then
           MsgBox "Kann MS Base Provider nicht finden!", vbExclamation, "Fehler:"

       'bestehenden RSA KeyExchange Schlüssel ermitteln:
       ElseIf CryptGetUserKey(hCryptProvA, AT_KEYEXCHANGE, hPrivateKey) = 0 Then
           MsgBox "Kann auf bestehenden Schlüssel nicht zugreifen!", vbExclamation, "Fehler:"
       End If
   Else
       'neuen RSA KeyExchange Schlüssel erzeugen:
       If CryptGenKey(hCryptProvA, CALG_RSA_KEYX, CRYPT_EXPORTABLE, hPrivateKey) = 0 Then
           MsgBox "Kann Schlüssel nicht erstellen!", vbExclamation, "Fehler:"
       End If
   End If


   '--------------------------------------------------------------------------------------
   'Öffentlichen Teil des KeyExchange Schlüssels exportieren:
   If CryptExportKey(hPrivateKey, 0, PUBLICKEYBLOB, 0, ByVal 0, cbData) = 0 Then
       MsgBox "Kann Schlüssel Länge nicht ermitteln!", vbExclamation, "Fehler:"
   Else
       'Speicher reservieren und Schlüsseldaten abholen:
       ReDim Preserve btPublicKey(cbData - 1)
       If CryptExportKey(hPrivateKey, 0, PUBLICKEYBLOB, 0, btPublicKey(0), cbData) = 0 Then
           MsgBox "Kann Schlüssel nicht exportieren!", vbExclamation, "Fehler:"
       End If
   End If

   '<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
   'Die öffentlichen Schlüsseldaten werden nun an den Partner B übermittelt, dort importiert,
   'ein zufälliger symmetrischer Sessionkey erstellt und dieser exportiert wobei die
   'Schlüsseldaten mit dem öffentlichen Schlüssel von Partner A verschlüsselt werden:

   '--------------------------------------------------------------------------------------
   If CryptAcquireContext(hCryptProvB, "Mein Container B", MS_DEF_PROV, PROV_RSA_FULL, CRYPT_NEWKEYSET) = 0 Then
       'Fehler->Existiert der Container bereits?
       If CryptAcquireContext(hCryptProvB, "Mein Container B", MS_DEF_PROV, PROV_RSA_FULL, 0) = 0 Then
           MsgBox "Kann MS Base Provider nicht finden!", vbExclamation, "Fehler:"
       End If
   End If
   
   'Öffentlichen Schlüssel importieren:
   If CryptImportKey(hCryptProvB, btPublicKey(0), UBound(btPublicKey) + 1, 0, 0, hPublicKey) = 0 Then
       MsgBox "Kann Schlüssel nicht importieren!", vbExclamation, "Fehler:"

   'Sessionkey erstellen:
   ElseIf CryptGenKey(hCryptProvB, CALG_DES, CRYPT_EXPORTABLE Or CRYPT_NO_SALT, hSessionKeyB) = 0 Then
       MsgBox "Kann Sessionkey nicht erstellen!", vbExclamation, "Fehler:"

   'Sessionkey exportieren:
   ElseIf CryptExportKey(hSessionKeyB, hPublicKey, SIMPLEBLOB, 0, ByVal 0, cbData) <> 0 Then
       ReDim btSessionKeyData(cbData - 1)
       If CryptExportKey(hSessionKeyB, hPublicKey, SIMPLEBLOB, 0, btSessionKeyData(0), cbData) = 0 Then
           MsgBox "Kann Sessionkey nicht exportieren!", vbExclamation, "Fehler:"
       
       'der Public Key wird nicht mehr benötigt -> zerstören:
       ElseIf CryptDestroyKey(hPublicKey) = 0 Then
           MsgBox "Kann Public Key nicht zerstören!", vbExclamation, "Fehler:"
       End If
   End If
   '<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
   'Die Daten des symmetrischen Sessionkeys werden nun zurück an den Partner A übermittelt,
   'dort importiert, und nun besitzen beide Partner den selben Schlüssel der zum Austausch
   'der Informationen verwendet werden kann:

   'Sessionkey importieren (mit private key entschlüsseln):
   If CryptImportKey(hCryptProvA, btSessionKeyData(0), _
           UBound(btSessionKeyData) + 1, hPrivateKey, 0, hSessionKeyA) = 0 Then
       MsgBox "Kann Sessionkey nicht importieren!", vbExclamation, "Fehler:"
   
   'der KeyExchange Schlüssel wird nun nicht mehr benötigt:
   ElseIf CryptDestroyKey(hPrivateKey) = 0 Then
       MsgBox "Kann Private Key nicht zerstören!", vbExclamation, "Fehler:"
   End If
   

   btData = "Hello World!"
   'Länge der verschlüsselten Daten ermitteln:
   cbData = UBound(btData) + 1
   If CryptEncrypt(hSessionKeyA, 0, 1, 0, 0, cbData, 0) = 0 Then
       MsgBox "Kann Länge nicht ermitteln!", vbExclamation, "Fehler:"
   Else
       'Speicher reservieren und verschlüsselte Daten abholen:
       x = UBound(btData) + 1
       ReDim Preserve btData(cbData - 1)
       cbData = x
       If CryptEncrypt(hSessionKeyA, 0, 1, 0, VarPtr(btData(0)), cbData, UBound(btData) + 1) = 0 Then
           MsgBox "Kann Daten nicht verschlüsseln!", vbExclamation, "Fehler:"
       Else
           'jetzt wieder entschlüsseln:
           If CryptDecrypt(hSessionKeyB, 0, 1, 0, VarPtr(btData(0)), cbData) = 0 Then
               MsgBox "Kann Daten nicht entschlüsseln!", vbExclamation, "Fehler:"
           Else
               ReDim Preserve btData(cbData - 1)
               MsgBox "Wieder entschlüsselt: " & CStr(btData), vbInformation, "Erfolgreich:"
           End If
       End If
   End If
   If hSessionKeyA <> 0 Then CryptDestroyKey hSessionKeyA
   If hSessionKeyB <> 0 Then CryptDestroyKey hSessionKeyB
   If hCryptProvA <> 0 Then CryptReleaseContext hCryptProvA, 0
   If hCryptProvB <> 0 Then CryptReleaseContext hCryptProvB, 0
   CryptAcquireContext hCryptProvA, "Mein Container B", MS_DEF_PROV, PROV_RSA_FULL, CRYPT_DELETEKEYSET
   CryptAcquireContext hCryptProvB, "Mein Container A", MS_DEF_PROV, PROV_RSA_FULL, CRYPT_DELETEKEYSET

End Sub

</vb>

Das folgende Beispiel zeigt den Schlüsseltausch mit Hilfe des Diffie-Hellman Algorithmus: <vb> Option Explicit

Private Declare Function CryptAcquireContext Lib "advapi32.dll" _

                Alias "CryptAcquireContextA" ( _
                ByRef phProv As Long, _
                ByVal pszContainer As String, _
                ByVal pszProvider As String, _
                ByVal dwProvType As Long, _
                ByVal dwFlags As Long) As Long

Private Declare Function CryptReleaseContext Lib "advapi32.dll" ( _

                ByVal hProv As Long, _
                ByVal dwFlags As Long) As Long

Private Declare Function CryptDestroyKey Lib "advapi32.dll" ( _

                ByVal hKey As Long) As Long

Private Declare Function CryptGenKey Lib "advapi32.dll" ( _

                ByVal hProv As Long, _
                ByVal AlgID As Long, _
                ByVal dwFlags As Long, _
                ByRef phKey As Long) As Long

Private Declare Function CryptExportKey Lib "advapi32.dll" ( _

                ByVal hKey As Long, _
                ByVal hExhKey As Long, _
                ByVal dwBlobType As Long, _
                ByVal dwFlags As Long, _
                ByRef pbData As Any, _
                ByRef pdwDataLen As Long) As Long

Private Declare Function CryptImportKey Lib "advapi32.dll" ( _

                ByVal hProv As Long, _
                ByRef pbData As Any, _
                ByVal dwDataLen As Long, _
                ByVal hPubKey As Long, _
                ByVal dwFlags As Long, _
                ByRef phKey As Long) As Long

Private Declare Function CryptEncrypt Lib "advapi32.dll" ( _

                ByVal hKey As Long, _
                ByVal hHash As Long, _
                ByVal Final As Long, _
                ByVal dwFlags As Long, _
                ByVal pbData As Long, _
                ByRef pdwDataLen As Long, _
                ByVal dwBufLen As Long) As Long

Private Declare Function CryptDecrypt Lib "advapi32.dll" ( _

                ByVal hKey As Long, _
                ByVal hHash As Long, _
                ByVal Final As Long, _
                ByVal dwFlags As Long, _
                ByVal pbData As Long, _
                ByRef pdwDataLen As Long) As Long

Private Declare Function CryptSetKeyParam Lib "advapi32.dll" ( _

               ByVal hKey As Long, _
               ByVal dwParam As Long, _
               ByRef pbData As Any, _
               ByVal dwFlags As Long) As Long

Private Declare Function CryptGetKeyParam Lib "advapi32.dll" ( _

               ByVal hKey As Long, _
               ByVal dwParam As Long, _
               ByRef pbData As Any, _
               ByRef pdwDataLen As Long, _
               ByVal dwFlags As Long) As Long
 

Private Type CRYPT_DATA_BLOB_VB

   cbData As Long
   pbData As Long
   Data() As Byte

End Type

Private Const MS_DEF_PROV As String = _

                   "Microsoft Base Cryptographic Provider v1.0"

Private Const CRYPT_NEWKEYSET As Long = &H8 Private Const CRYPT_EXPORTABLE As Long = &H1 Private Const CRYPT_NO_SALT As Long = &H10 Private Const CRYPT_DELETEKEYSET As Long = &H10 Private Const CRYPT_PREGEN As Long = &H40

Private Const PUBLICKEYBLOB As Long = &H6

Private Const KP_ALGID As Long = 7 Private Const KP_P As Long = 11 Private Const KP_G As Long = 12 Private Const KP_X As Long = 14


Private Const ALG_CLASS_KEY_EXCHANGE As Long = &HA000& Private Const ALG_CLASS_HASH As Long = &H8000& Private Const ALG_CLASS_DATA_ENCRYPT As Long = &H6000& Private Const ALG_CLASS_SIGNATURE As Long = &H2000&

Private Const ALG_TYPE_ANY As Long = 0 Private Const ALG_TYPE_RSA As Long = &H400& Private Const ALG_TYPE_BLOCK As Long = &H600& Private Const ALG_TYPE_STREAM As Long = &H800& Private Const ALG_TYPE_DH As Long = &HA00&

Private Const ALG_SID_RSA_ANY As Long = 0 Private Const ALG_SID_DH_SANDF As Long = 1 ' Diffie-Hellman Private Const ALG_SID_DH_EPHEM As Long = 2 ' Diffie-Hellman

Private Const ALG_SID_MD2 As Long = 1 Private Const ALG_SID_MD4 As Long = 2 Private Const ALG_SID_MD5 As Long = 3 Private Const ALG_SID_SHA As Long = 4 Private Const ALG_SID_SHA_256 As Long = 12 Private Const ALG_SID_SHA_384 As Long = 13 Private Const ALG_SID_SHA_512 As Long = 14

Private Const ALG_SID_RC4 As Long = 1 Private Const ALG_SID_DES As Long = 1 Private Const ALG_SID_RC2 As Long = 2 Private Const ALG_SID_3DES As Long = 3 Private Const ALG_SID_3DES_112 As Long = 9 Private Const ALG_SID_AES_128 As Long = 14 Private Const ALG_SID_AES_192 As Long = 15 Private Const ALG_SID_AES_256 As Long = 16 Private Const ALG_SID_AES As Long = 17

'Encryption (symmetrisch): Private Enum EnmCryptAlgo

   CALG_RC2 = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_RC2)
   CALG_RC4 = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_STREAM Or ALG_SID_RC4)
   CALG_DES = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_DES)
   CALG_3DES = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_3DES)
   CALG_3DES_112 = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_3DES_112)
   CALG_AES_128 = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_AES_128)
   CALG_AES_192 = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_AES_192)
   CALG_AES_256 = (ALG_CLASS_DATA_ENCRYPT Or ALG_TYPE_BLOCK Or ALG_SID_AES_256)

End Enum

'Keyexchange and Signature Algorithmen (asymmetrisch): Private Enum EnmKeyTypes

   CALG_RSA_SIGN = (ALG_CLASS_SIGNATURE Or ALG_TYPE_RSA Or ALG_SID_RSA_ANY)
   CALG_RSA_KEYX = (ALG_CLASS_KEY_EXCHANGE Or ALG_TYPE_RSA Or ALG_SID_RSA_ANY)
   CALG_DH_SF = (ALG_CLASS_KEY_EXCHANGE Or ALG_TYPE_DH Or ALG_SID_DH_SANDF)
   CALG_DH_EPHEM = (ALG_CLASS_KEY_EXCHANGE Or ALG_TYPE_DH Or ALG_SID_DH_EPHEM)

End Enum

Private Const MS_ENH_DSS_DH_PROV As String = _

                   "Microsoft Enhanced DSS and Diffie-Hellman Cryptographic Provider"

Private Const PROV_DSS_DH As Long = 13


Private Sub Command1_Click()

   Dim hCryptProvA As Long
   Dim hPrivateKeyA As Long
   Dim btPublicKeyA() As Byte
   Dim hSessionKeyA As Long
   
   Dim hCryptProvB As Long
   Dim hPrivateKeyB As Long
   Dim btPublicKeyB() As Byte
   Dim hSessionKeyB As Long
   
   Dim cbData As Long
   Dim btData() As Byte
   Dim x As Long
   
   Dim P_Blob As CRYPT_DATA_BLOB_VB
   Dim G_Blob As CRYPT_DATA_BLOB_VB
   
   Const KEY_LENGTH As Long = 1024
   
   'etwaige alte Container löschen
   CryptAcquireContext hCryptProvA, "Mein Container B", MS_ENH_DSS_DH_PROV, PROV_DSS_DH, CRYPT_DELETEKEYSET
   CryptAcquireContext hCryptProvB, "Mein Container A", MS_ENH_DSS_DH_PROV, PROV_DSS_DH, CRYPT_DELETEKEYSET
   
   
   '<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
   'Partner A erstellt einen D-H KeyExchange Schlüssel und exportiert den öffentlichen
   'Schlüsselteil sowie die Parameter P und G:
   '--------------------------------------------------------------------------------------
   'Provider Kontext anfordern und Schlüssel erstellen:
   If CryptAcquireContext(hCryptProvA, "Mein Container A", MS_ENH_DSS_DH_PROV, PROV_DSS_DH, CRYPT_NEWKEYSET) = 0 Then
       MsgBox "Kann Provider Kontext nicht öffnen!", vbExclamation, "Fehler:"
   ElseIf CryptGenKey(hCryptProvA, CALG_DH_SF, KEY_LENGTH * &H10000 Or CRYPT_EXPORTABLE, hPrivateKeyA) = 0 Then
       MsgBox "Kann Schlüssel nicht erstellen!", vbExclamation, "Fehler:"
   End If

   '--------------------------------------------------------------------------------------
   'Öffentlichen Teil des KeyExchange Schlüssels exportieren:
   If CryptExportKey(hPrivateKeyA, 0, PUBLICKEYBLOB, 0, ByVal 0, cbData) = 0 Then
       MsgBox "Kann Schlüssel Länge nicht ermitteln!", vbExclamation, "Fehler:"
   Else
       'Speicher reservieren und Schlüsseldaten abholen:
       ReDim Preserve btPublicKeyA(cbData - 1)
       If CryptExportKey(hPrivateKeyA, 0, PUBLICKEYBLOB, 0, btPublicKeyA(0), cbData) = 0 Then
           MsgBox "Kann Schlüssel nicht exportieren!", vbExclamation, "Fehler:"
       End If
   End If

   '--------------------------------------------------------------------------------------
   'P und G exportieren:
   ReDim P_Blob.Data(KEY_LENGTH / 8 - 1)
   P_Blob.cbData = KEY_LENGTH / 8
   P_Blob.pbData = VarPtr(P_Blob.Data(0))

   ReDim G_Blob.Data(KEY_LENGTH / 8 - 1)
   G_Blob.cbData = KEY_LENGTH / 8
   G_Blob.pbData = VarPtr(G_Blob.Data(0))

   If CryptGetKeyParam(hPrivateKeyA, KP_G, G_Blob.Data(0), G_Blob.cbData, 0) = 0 Then
       MsgBox "Kann G nicht lesen!", vbExclamation, "Fehler:"
   ElseIf CryptGetKeyParam(hPrivateKeyA, KP_P, P_Blob.Data(0), P_Blob.cbData, 0) = 0 Then
       MsgBox "Kann P nicht lesen!", vbExclamation, "Fehler:"
   End If
   
   '<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
   'Die öffentlichen Schlüsseldaten, P und G werden nun an den Partner B übermittelt.
   'Partner B erstellt seinerseits einen D-H KeyExchange Schlüssel mit den erhaltenen
   'Parametern P und G, exportiert den öffentlichen Schlüsselteil und übermittelt diesen
   'an Partner A:

   '--------------------------------------------------------------------------------------
   'Provider Kontext anfordern und Schlüssel erstellen:
   If CryptAcquireContext(hCryptProvB, "Mein Container B", MS_ENH_DSS_DH_PROV, PROV_DSS_DH, CRYPT_NEWKEYSET) = 0 Then
       MsgBox "Kann Provider Kontext nicht öffnen!", vbExclamation, "Fehler:"
   ElseIf CryptGenKey(hCryptProvB, CALG_DH_SF, KEY_LENGTH * &H10000 Or CRYPT_EXPORTABLE Or CRYPT_PREGEN, hPrivateKeyB) = 0 Then
       MsgBox "Kann Schlüssel nicht erstellen!", vbExclamation, "Fehler:"
   End If
   
   '--------------------------------------------------------------------------------------
   'P und G importieren:
   If CryptSetKeyParam(hPrivateKeyB, KP_G, G_Blob, 0) = 0 Then
       MsgBox "Kann G nicht setzen!", vbExclamation, "Fehler:"
   ElseIf CryptSetKeyParam(hPrivateKeyB, KP_P, P_Blob, 0) = 0 Then
       MsgBox "Kann P nicht setzen!", vbExclamation, "Fehler:"
   ElseIf CryptSetKeyParam(hPrivateKeyB, KP_X, ByVal 0, 0) = 0 Then
       MsgBox "Kann X nicht generieren!", vbExclamation, "Fehler:"
   End If
   
   '--------------------------------------------------------------------------------------
   'Öffentlichen Teil des KeyExchange Schlüssels exportieren:
   If CryptExportKey(hPrivateKeyB, 0, PUBLICKEYBLOB, 0, ByVal 0, cbData) = 0 Then
       MsgBox "Kann Schlüssel Länge nicht ermitteln!", vbExclamation, "Fehler:"
   Else
       'Speicher reservieren und Schlüsseldaten abholen:
       ReDim Preserve btPublicKeyB(cbData - 1)
       If CryptExportKey(hPrivateKeyB, 0, PUBLICKEYBLOB, 0, btPublicKeyB(0), cbData) = 0 Then
           MsgBox "Kann Schlüssel nicht exportieren!", vbExclamation, "Fehler:"
       End If
   End If
   
   '<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
   'Beide öffentlichen Schlüsseldaten werden nun importiert und der gemeinsame Sessionkey
   'kann daraus ermittelt werden:
   
   '--------------------------------------------------------------------------------------
   'Öffentliche Schlüssel importieren:
   If CryptImportKey(hCryptProvB, btPublicKeyA(0), UBound(btPublicKeyA) + 1, hPrivateKeyB, 0, hSessionKeyB) = 0 Then
       MsgBox "Kann Schlüssel A nicht importieren!", vbExclamation, "Fehler:"
   ElseIf CryptImportKey(hCryptProvA, btPublicKeyB(0), UBound(btPublicKeyB) + 1, hPrivateKeyA, 0, hSessionKeyA) = 0 Then
       MsgBox "Kann Schlüssel B nicht importieren!", vbExclamation, "Fehler:"
   End If
   
   '--------------------------------------------------------------------------------------
   'zu Sessionkey umwandeln:
   If CryptSetKeyParam(hSessionKeyA, KP_ALGID, CALG_RC4, 0) = 0 Then
        MsgBox "Kann Schlüssel nicht umwandeln!", vbExclamation, "Fehler:"
   ElseIf CryptSetKeyParam(hSessionKeyB, KP_ALGID, CALG_RC4, 0) = 0 Then
        MsgBox "Kann Schlüssel nicht umwandeln!", vbExclamation, "Fehler:"
   End If

   '--------------------------------------------------------------------------------------
   'die D-H Schlüssel werden nun nicht mehr benötigt:
   CryptDestroyKey hPrivateKeyA
   CryptDestroyKey hPrivateKeyB




   '--------------------------------------------------------------------------------------
   'Test:
   btData = "Hello World!"
   'Länge der verschlüsselten Daten ermitteln:
   cbData = UBound(btData) + 1
   If CryptEncrypt(hSessionKeyA, 0, 1, 0, 0, cbData, 0) = 0 Then
       MsgBox "Kann Länge nicht ermitteln!", vbExclamation, "Fehler:"
   Else
       'Speicher reservieren und verschlüsselte Daten abholen:
       x = UBound(btData) + 1
       ReDim Preserve btData(cbData - 1)
       cbData = x
       If CryptEncrypt(hSessionKeyA, 0, 1, 0, VarPtr(btData(0)), cbData, UBound(btData) + 1) = 0 Then
           MsgBox "Kann Daten nicht verschlüsseln!", vbExclamation, "Fehler:"
       Else
           'jetzt wieder entschlüsseln:
           If CryptDecrypt(hSessionKeyB, 0, 1, 0, VarPtr(btData(0)), cbData) = 0 Then
               MsgBox "Kann Daten nicht entschlüsseln!", vbExclamation, "Fehler:"
           Else
               ReDim Preserve btData(cbData - 1)
               MsgBox "Wieder entschlüsselt: " & CStr(btData), vbInformation, "Erfolgreich:"
           End If
       End If
   End If
   If hSessionKeyA <> 0 Then CryptDestroyKey hSessionKeyA
   If hSessionKeyB <> 0 Then CryptDestroyKey hSessionKeyB
   If hCryptProvA <> 0 Then CryptReleaseContext hCryptProvA, 0
   If hCryptProvB <> 0 Then CryptReleaseContext hCryptProvB, 0

End Sub </vb>