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Add an S/MIME Detached Signature

Demonstrates the Chilkat Mime.AddDetachedSignature method, which creates an S/MIME detached signature. The only argument is the signing Cert, which must have access to its private key. On success the entity becomes a multipart/signed with the content and a separate signature part.

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: A detached signature (multipart/signed) keeps the original content readable alongside a separate signature part — so recipients whose software does not understand S/MIME still see the message, they just cannot verify it. That backward compatibility makes detached the usual choice for signed email. The signer proves authorship with a certificate that carries its private key.

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LOCAL nSuccess
LOCAL oMime
LOCAL cPfxPassword
LOCAL oCert

nSuccess := 0

oMime := CreateObject("Chilkat.Mime")
nSuccess := oMime:SetBodyFromPlainText("This message will be signed.")
IF (nSuccess == 0)
    ? oMime:LastErrorText
    oMime:destroy()
    RETURN
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.
cPfxPassword := "myPfxPassword"
oCert := CreateObject("Chilkat.Cert")
nSuccess := oCert:LoadPfxFile("qa_data/signer.pfx", cPfxPassword)
IF (nSuccess == 0)
    ? oCert:LastErrorText
    oMime:destroy()
    oCert:destroy()
    RETURN
ENDIF

//  Create an S/MIME detached signature.  The object becomes a multipart/signed entity with the
//  original content and a separate signature part.
nSuccess := oMime:AddDetachedSignature(oCert)
IF (nSuccess == 0)
    ? oMime:LastErrorText
    oMime:destroy()
    oCert:destroy()
    RETURN
ENDIF

nSuccess := oMime:SaveMime("qa_output/signed.eml")
IF (nSuccess == 0)
    ? oMime:LastErrorText
    oMime:destroy()
    oCert:destroy()
    RETURN
ENDIF

? "Detached signature added."

oMime:destroy()
oCert:destroy()