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Create an Opaque (Attached) S/MIME Signature

Demonstrates the Chilkat Mime.ConvertToSigned method, which creates an opaque (attached) S/MIME signature. The only argument is the signing Cert. On success the entity is replaced by a CMS/PKCS #7 signed-data structure that wraps the content inside the signature.

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: An opaque signature bundles the content inside the CMS structure, so the message is a single application/pkcs7-mime blob that only S/MIME-aware software can read. It is more tamper-resistant in transit — nothing can alter the content without breaking the wrapper — at the cost of the backward compatibility a detached signature offers. Use it when every recipient is known to support S/MIME.

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Local $bSuccess = False

$oMime = ObjCreate("Chilkat.Mime")
$bSuccess = $oMime.SetBodyFromPlainText("This message will be signed.")
If ($bSuccess = False) Then
    ConsoleWrite($oMime.LastErrorText & @CRLF)
    Exit
EndIf

;  Load the signing certificate (which must have access to its private key) from a PFX file.
;  The PFX password should come from a secure source rather than being hard-coded.
Local $sPfxPassword = "myPfxPassword"
$oCert = ObjCreate("Chilkat.Cert")
$bSuccess = $oCert.LoadPfxFile("qa_data/signer.pfx",$sPfxPassword)
If ($bSuccess = False) Then
    ConsoleWrite($oCert.LastErrorText & @CRLF)
    Exit
EndIf

;  Create an OPAQUE (attached) S/MIME signature.  The entity is replaced by a CMS/PKCS #7
;  signed-data structure that wraps the content inside the signature.
$bSuccess = $oMime.ConvertToSigned($oCert)
If ($bSuccess = False) Then
    ConsoleWrite($oMime.LastErrorText & @CRLF)
    Exit
EndIf

$bSuccess = $oMime.SaveMime("qa_output/signed_opaque.eml")
If ($bSuccess = False) Then
    ConsoleWrite($oMime.LastErrorText & @CRLF)
    Exit
EndIf

ConsoleWrite("Message converted to an opaque signed message." & @CRLF)