(.NET Core C#) Send a Signed Email using RSASSA-PSS with SHA256

Demonstrates how to sign and send an email using the RSASSA-PSS signing algorithm with the SHA256 hash algorithm.

Note: This example requires Chilkat v9.5.0.67 or greater.

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

// Get a digital certificate with private key from a .pfx
// (Chilkat has many different ways to provide a cert + private key for siging.
// Using a PFX is just one possible option.)
Chilkat.Pfx pfx = new Chilkat.Pfx();
bool success = pfx.LoadPfxFile("qa_data/rsassa-pss/privatekey.pfx","PFX_PASSWORD");
if (success != true) {
    Debug.WriteLine(pfx.LastErrorText);
    return;
}

Chilkat.Email email = new Chilkat.Email();

// Create a simple email.
email.Subject = "Sample RSASSA-PSS Signed Email";
email.Body = "Sample RSASSA-PSS Signed Email";
email.From = "from_name@mydomain.com";
// Add one ore more recipients..
email.AddTo("Chilkat Support","support@chilkatsoft.com");
email.AddTo("Chilkat GMail","chilkat.support@gmail.com");

// Indicate that the email is to be signed, and that we want to use RSASSA-PSS.
email.SendSigned = true;
email.SigningAlg = "pss";
email.SigningHashAlg = "sha256";

// Get the certificate to be used for signing.
// (The typical case for a PFX is that it contains a cert with an associated private key,
// as well as other certificates in the chain of authentication.  The cert with the private
// key should be in the first position at index 0.)
Chilkat.Cert cert = pfx.GetCert(0);
if (pfx.LastMethodSuccess != true) {
    Debug.WriteLine(pfx.LastErrorText);
    return;
}

// Tell the email object to use this cert (and private key) for signing.
email.SetSigningCert(cert);

Chilkat.MailMan mailman = new Chilkat.MailMan();

// Set the SMTP settings for your email account on your mail server.
mailman.SmtpUsername = "SMTP_LOGIN";
mailman.SmtpPassword = "SMTP_PASSWORD";
mailman.SmtpHost = "MY_SMTP_DOMAIN_OR_IP";
mailman.SmtpPort = 587;
mailman.StartTLS = true;

// Signed email can be sent in two different ways.  
// In a multipart/signed email, the signature is attached as a separate MIME part.
// In an opaque email (signedData) the content of the email is encapsulated within the signature
// and the email is sent as "application/pkcs7-mime". 
// Either should be fine, but some receiving systems might require one or the other..
mailman.OpaqueSigning = false;

// Send the email.  The mailman will sign the email as directed by the 
// property settings of the email object.
success = mailman.SendEmail(email);
if (success != true) {
    Debug.WriteLine(mailman.LastErrorText);
    return;
}

success = mailman.CloseSmtpConnection();
if (success != true) {
    Debug.WriteLine("Connection to SMTP server not closed cleanly.");
}

Debug.WriteLine("Mail Sent!");

// -----------------------------------------------------------
// This is the MIME of the RSASSA-PSS signed email that was sent

// 	MIME-Version: 1.0
// 	Date: Thu, 20 Apr 2017 10:14:58 -0500
// 	Message-ID: <3682A87344CB3A4FB5EB5BC9908C0C4DA01DA461@CHILKAT13>
// 	Content-Type: multipart/signed; protocol="application/pkcs7-signature"; micalg=sha256;
// 	 boundary="------------050103020705000601010800"
// 	X-Priority: 3 (Normal)
// 	Subject: Sample RSASSA-PSS Signed Email
// 	From: support@chilkatsoft.com
// 	To: "Chilkat Support" <support@chilkatsoft.com>,
// 	 "Chilkat GMail" <chilkat.support@gmail.com>
// 
// 	--------------050103020705000601010800
// 	Content-Type: text/plain; format=flowed
// 	Content-Transfer-Encoding: 7bit
// 
// 	Sample RSASSA-PSS Signed Email
// 	--------------050103020705000601010800
// 	Content-Transfer-Encoding: base64
// 	Content-Type: application/pkcs7-signature; name="smime.p7s"
// 	Content-Disposition: attachment; filename="smime.p7s"
// 
// 	MIIG5wYJKoZIhvcNAQcCoIIG2DCCBtQCAQExDzANBglghkgBZQMEAgEFADALBgkqhkiG9w0BBwGg
// 	ggL4MIIC9DCCAl2gAwIBAgIJAMPsJCT11cniMA0GCSqGSIb3DQEBCwUAMIGSMQswCQYDVQQGEwJB
// 	VTERMA8GA1UECAwIVmljdG9yaWExEjAQBgNVBAcMCU1lbGJvdXJuZTEhMB8GA1UECgwYSW50ZXJu
// 	ZXQgV2lkZ2l0cyBQdHkgTHRkMQ8wDQYDVQQDDAZXaWRnZXQxKDAmBgkqhkiG9w0BCQEWGWFkbWlu
// 	QGludGVybmV0d2lkZ2V0cy5jb20wHhcNMTYxMTAxMTY1MjMyWhcNMjExMDMxMTY1MjMyWjCBkjEL
// 	MAkGA1UEBhMCQVUxETAPBgNVBAgMCFZpY3RvcmlhMRIwEAYDVQQHDAlNZWxib3VybmUxITAfBgNV
// 	BAoMGEludGVybmV0IFdpZGdpdHMgUHR5IEx0ZDEPMA0GA1UEAwwGV2lkZ2V0MSgwJgYJKoZIhvcN
// 	AQkBFhlhZG1pbkBpbnRlcm5ldHdpZGdldHMuY29tMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKB
// 	gQDGIdoCjyavs+F/Rm0VIB4m6O7VL1j+1IqieoR9NEX2GQvu2VCdceyxf9qaw1bxipEvjLwUkw7M
// 	e+BTlLpWQbBMH87s6KpsC8MVyXhMLpP0oM8NFix/vLz2wdLhUh7CZvJA0plqkJk9bj57QIu+EO1k
// 	tUHM2DFb6sckvCL2yybD1wIDAQABo1AwTjAdBgNVHQ4EFgQUONKKu2zsXIrinWxIGT654vrcQwsw
// 	HwYDVR0jBBgwFoAUONKKu2zsXIrinWxIGT654vrcQwswDAYDVR0TBAUwAwEB/zANBgkqhkiG9w0B
// 	AQsFAAOBgQArFvdi5u9i2QF1Qw+cdC1l7w2Y3+q6RIkln2W8rWJFje00644o8hXy7v46giJCedmF
// 	ULlhm1n7XIsZGy2W3lJ77v5agn9gFwXu1h3cqkGXkoteE6SQJQXWgsW3GWPveObvTL8LF4y57fgM
// 	9ZWS+V9MJajeu44Rf/tU17TLYKjvEjGCA7MwggOvAgEBMIGgMIGSMQswCQYDVQQGEwJBVTERMA8G
// 	A1UECAwIVmljdG9yaWExEjAQBgNVBAcMCU1lbGJvdXJuZTEhMB8GA1UECgwYSW50ZXJuZXQgV2lk
// 	Z2l0cyBQdHkgTHRkMQ8wDQYDVQQDDAZXaWRnZXQxKDAmBgkqhkiG9w0BCQEWGWFkbWluQGludGVy
// 	bmV0d2lkZ2V0cy5jb20CCQDD7CQk9dXJ4jANBglghkgBZQMEAgEFAKCCAjQwGAYJKoZIhvcNAQkD
// 	MQsGCSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMTcwNDIwMTUxNDU4WjAvBgkqhkiG9w0BCQQx
// 	IgQgoHOtpFiAgti0cwDw46C8wyYSZbhx2yJqJZ/qRE8WPSQwXwYJKoZIhvcNAQkPMVIwUDALBglg
// 	hkgBZQMEAQIwCgYIKoZIhvcNAwcwDgYIKoZIhvcNAwICAgCAMA0GCCqGSIb3DQMCAgFAMAcGBSsO
// 	AwIHMA0GCCqGSIb3DQMCAgEoMIGxBgkrBgEEAYI3EAQxgaMwgaAwgZIxCzAJBgNVBAYTAkFVMREw
// 	DwYDVQQIDAhWaWN0b3JpYTESMBAGA1UEBwwJTWVsYm91cm5lMSEwHwYDVQQKDBhJbnRlcm5ldCBX
// 	aWRnaXRzIFB0eSBMdGQxDzANBgNVBAMMBldpZGdldDEoMCYGCSqGSIb3DQEJARYZYWRtaW5AaW50
// 	ZXJuZXR3aWRnZXRzLmNvbQIJAMPsJCT11cniMIGzBgsqhkiG9w0BCRACCzGBo6CBoDCBkjELMAkG
// 	A1UEBhMCQVUxETAPBgNVBAgMCFZpY3RvcmlhMRIwEAYDVQQHDAlNZWxib3VybmUxITAfBgNVBAoM
// 	GEludGVybmV0IFdpZGdpdHMgUHR5IEx0ZDEPMA0GA1UEAwwGV2lkZ2V0MSgwJgYJKoZIhvcNAQkB
// 	FhlhZG1pbkBpbnRlcm5ldHdpZGdldHMuY29tAgkAw+wkJPXVyeIwPQYJKoZIhvcNAQEKMDCgDTAL
// 	BglghkgBZQMEAgGhGjAYBgkqhkiG9w0BAQgwCwYJYIZIAWUDBAIBogMCASAEgYCDQpT6vJZ9zERJ
// 	JVX69PGUfCN5Eq9pKzoOTQSrIBe1YgNDSPd5pyOPP2MN1RpI0T/GTQZw4iWy5LZq0T5sjmk3fFVB
// 	+VZjKtkTuhGaCdzMQXomVLBbI2fN4UaA4v1/Ayrqr8SY9Rsa20TpKv/bufK7oYs083UOtlcA1EHY
// 	41wQ5A==
// 
// 	--------------050103020705000601010800--