Perl

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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Perl

use chilkat();

$success = 0;

$mime = chilkat::CkMime->new();
$success = $mime->SetBodyFromPlainText("This message will be signed.");
if ($success == 0) {
    print $mime->lastErrorText() . "\r\n";
    exit;
}

#  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.
$pfxPassword = "myPfxPassword";
$cert = chilkat::CkCert->new();
$success = $cert->LoadPfxFile("qa_data/signer.pfx",$pfxPassword);
if ($success == 0) {
    print $cert->lastErrorText() . "\r\n";
    exit;
}

#  Create an S/MIME detached signature.  The object becomes a multipart/signed entity with the
#  original content and a separate signature part.
$success = $mime->AddDetachedSignature($cert);
if ($success == 0) {
    print $mime->lastErrorText() . "\r\n";
    exit;
}

$success = $mime->SaveMime("qa_output/signed.eml");
if ($success == 0) {
    print $mime->lastErrorText() . "\r\n";
    exit;
}

print "Detached signature added." . "\r\n";