(.NET Core C#) CoSign PKCS7/CMS Signed Data

See more Digital Signatures Examples

Demonstrates how to add a 2nd signature to a CMS SignedData. This is to add an additional signature, SignerInfo and certificate(s) to an existing CMS signed data.

In this example, we cosign an existing pdf.p7s

Note: The CoSign method is added in Chilkat v9.5.0.89.

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// This example assumes the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

Chilkat.Crypt2 crypt = new Chilkat.Crypt2();
Chilkat.Cert cert = new Chilkat.Cert();

// If loading from a smart card, set the smartcard PIN.
cert.SmartCardPin = "0000";

// Load a certificate in some way, such as from a smart card.
// Chilkat provides other methods to load from a .pfx, .pem, or from the Windows certificate stores..
bool success = cert.LoadFromSmartcard("");
if (success == false) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

success = crypt.SetSigningCert(cert);
if (success == false) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

// Load the file to be co-signed.
// NOTE:  This is to cosign a PDF file contained within a CMS (PKCS7) message.
// (In other words, the PDF is contained within the CMS SignedData, rather than the other way around
// where a CMS signature is contained within a PDF.  Use Chilkat's PDF class to sign a PDF, which is
// to embed a CMS signature within the PDF.)
Chilkat.BinData bd = new Chilkat.BinData();
success = bd.LoadFile("qa_data/p7s/cosign/sample.pdf.p7s");
if (success == false) {
    Debug.WriteLine("Failed to load pdf.p7s input file.");
    return;
}

// bd2 will contain the co-signed result.
Chilkat.BinData bd2 = new Chilkat.BinData();
success = crypt.CoSign(bd,cert,bd2);
if (success == false) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

success = bd.WriteFile("qa_output/cosigned.pdf.p7s");
if (success == false) {
    Debug.WriteLine("Failed to save pdf.p7s output file.");
    return;
}

Debug.WriteLine("Success!");