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. .
Chilkat C# Downloads

bool success = false;

//  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();
success = pfx.LoadPfxFile("qa_data/rsassa-pss/privatekey.pfx","PFX_PASSWORD");
if (success == false) {
    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 = new Chilkat.Cert();
success = pfx.CertAt(0,cert);
if (success == false) {
    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 == false) {
    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
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//  	41wQ5A==
//  
//  	--------------050103020705000601010800--