(C#) Create PKCS7 Detached Signature (S/MIME)

Create an S/MIME message with a PKCS7 detached signature.

Important: This example is specific to the Windows operating system because it obtains the certificate and private key from the Windows registry-based certificate store. For other operating systems, see the PKCS7 signature examples that use PFX (.p12) files.

Download: Chilkat .NET Assemblies

Chilkat.Mime mime = new Chilkat.Mime();

bool success;
success = mime.UnlockComponent("Anything for 30-day trial");
if (success == false) {
    textBox1.Text += mime.LastErrorText + "\r\n";
    return;
}

//  Load a certificate w/ private key for signing.
//  There are many ways of getting a certificate object:
//  from a pfx file, from .cer and private-key files, from the
//  Windows registry-based certificate stores, etc.
//  For this example, we'll use a pre-installed cert from
//  a certificate store.
Chilkat.Cert cert = new Chilkat.Cert();
success = cert.LoadByCommonName("Chilkat Software, Inc.");
if (success == false) {
    textBox1.Text += cert.LastErrorText + "\r\n";
    return;
}

//  Create a very simple MIME message to be signed:
mime.AddHeaderField("Subject","This is a test");
mime.AddHeaderField("MyCustomHeader","abc123");
mime.ContentType = "text/plain";
mime.SetBody("This is a plain-text body.");

//  Examine the MIME prior to signing:
textBox1.Text += "--- MIME prior to signing ---" + "\r\n";
textBox1.Text += mime.GetMime() + "\r\n";

//  The MIME prior to signing looks like this:
//  -------------------------------------------------------------------------------
//  
Subject: This is a test
MyCustomHeader: abc123
Content-Type: text/plain

This is a plain-text body.
//  -------------------------------------------------------------------------------

//  The default hash algorithm used in the signing process is "SHA1".
//  To change it, set the SigningHashAlg property:
mime.SigningHashAlg = "SHA256";

//  Add a detached signature:
success = mime.AddDetachedSignature(cert);
if (success == false) {
    textBox1.Text += mime.LastErrorText + "\r\n";
    return;
}

//  Examine the MIME with detached signature:
textBox1.Text += "--- MIME with detached signature ---" + "\r\n";
textBox1.Text += mime.GetMime() + "\r\n";

//  The MIME after signing looks like this:
//  -------------------------------------------------------------------------------
//  
Content-Type: multipart/signed;
 boundary="----=_NextPart_a66_7f43_247e22d0.a03166d5";
 protocol="application/x-pkcs7-signature"; micalg="sha256"

This is a multi-part message in MIME format.

------=_NextPart_a66_7f43_247e22d0.a03166d5
Subject: This is a test
MyCustomHeader: abc123
Content-Type: text/plain

This is a plain-text body.
------=_NextPart_a66_7f43_247e22d0.a03166d5
Content-Transfer-Encoding: base64
Content-Type: application/x-pkcs7-signature;
 name="smime.p7s"
Content-Disposition: attachment; filename="smime.p7s"
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==

------=_NextPart_a66_7f43_247e22d0.a03166d5--
//  -------------------------------------------------------------------------------