VB.NET

Get an S/MIME Signing Time

Demonstrates the Chilkat Mime.GetSignatureSigningTimeStr method, which returns the CMS signingTime attribute for the signer at a zero-based index, as an RFC 822-style date string in GMT. The only argument is the signer index.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: This is the timestamp the signer asserted at signing — useful for "when was this signed" audit trails and for evaluating whether the signing certificate was valid at that moment. Because it is a signed attribute, it is tamper-evident. Guard the call with HasSignatureSigningTime, since the attribute is optional. Note it is the signer's claim, not a trusted third-party timestamp.

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VB.NET

Dim success As Boolean = False

Dim mime As New Chilkat.Mime
success = mime.LoadMimeFile("qa_data/signed.eml")
If (success = False) Then
    Debug.WriteLine(mime.LastErrorText)
    Exit Sub
End If


'  After verifying, get the CMS signingTime for each signer that has one, as an RFC 822 date string
'  in GMT.  The only argument is the zero-based signer index.
success = mime.Verify()
If (success <> True) Then
    Debug.WriteLine(mime.LastErrorText)
    Exit Sub
End If


Dim n As Integer = mime.NumSignerCerts
Dim i As Integer
For i = 0 To n - 1
    '  Only signers that included a signing time have one to retrieve.
    If (mime.HasSignatureSigningTime(i)) Then
        Dim signingTime As String = mime.GetSignatureSigningTimeStr(i)
        If (mime.LastMethodSuccess = False) Then
            Debug.WriteLine(mime.LastErrorText)
            Exit Sub
        End If

        Debug.WriteLine("Signer " & i & " signing time: " & signingTime)
    End If

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