GCM_InitKey

Initializes the context with the key ready for repeated operations of GCM_NextEncrypt and GCM_NextDecrypt.

VB6/VBA

Debug.Print "Testing GCM_InitKey ..."
Dim abKey() As Byte
Dim nKeyLen As Long
Dim hContext As Long
Dim nCode As Long

' Initialise with a valid key
abKey = cnvBytesFromHexStr("feffe9928665731c6d6a8f9467308308")
nKeyLen = UBound(abKey) + 1
hContext = GCM_InitKey(abKey(0), nKeyLen, 0)
Debug.Print "GCM_InitKey returns " & Hex(hContext) & " (expected non-0)"
If hContext <> 0 Then
    '... do something here...
    ' Destroy the key
    Call GCM_FinishKey(hContext)
End If

' Now try an invalid key (length must be 16,24, or 32 bytes)
abKey = cnvBytesFromHexStr("badace")
nKeyLen = UBound(abKey) + 1
hContext = GCM_InitKey(abKey(0), nKeyLen, 0)
Debug.Print "GCM_InitKey returns " & Hex(hContext)
' Use API_ErrorCode to find the error value
nCode = API_ErrorCode()
Debug.Print "API_ErrorCode returns " & nCode & ": " & apiErrorLookup(nCode)

Output

Testing GCM_InitKey ...
GCM_InitKey returns 3FFE5A71 (expected non-0)
GCM_InitKey returns 0
API_ErrorCode returns 33: Invalid key length (BAD_KEY_LEN_ERROR)

VB.NET

Console.WriteLine("Testing GCM_InitKey ...")
Dim abKey() As Byte
Dim nKeyLen As Integer
''Dim hContext As Integer
Dim nCode As Integer
Dim nRet As Integer
Dim oGcm As Gcm = Gcm.Instance()

' Initialise with a valid key
abKey = Cnv.FromHex("feffe9928665731c6d6a8f9467308308")
nKeyLen = UBound(abKey) + 1
nRet = oGcm.InitKey(abKey)
Console.WriteLine("GCM_InitKey returns " & nRet & " (expected zero)")
If nRet = 0 Then
    '... do something here...
    ' Destroy the key
    oGcm.Dispose()
End If

' Now try an invalid key (length must be 16,24, or 32 bytes)
abKey = Cnv.FromHex("badace")
nKeyLen = UBound(abKey) + 1
nRet = oGcm.InitKey(abKey)
Console.WriteLine("GCM_InitKey returns " & nRet)
' Use API_ErrorCode to find the error value
nCode = oGcm.ErrCode()
Console.WriteLine("API_ErrorCode returns " & nCode & ": " & General.ErrorLookup(nCode))

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