Create S/MIME with Detached Signature

C# example to create a simple S/MIME message with a detached digital signature.

Download Chilkat .NET for 2.0 Framework

Download Chilkat .NET for 1.0 / 1.1 Framework

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

//  Any string argument automatically begins the 30-day trial.
bool success;
success = mime.UnlockComponent("30-day trial");
if (success != true) {
    MessageBox.Show("MIME component unlock failed");
    return;
}

//  Find our digital certificate from the Current User certificate store.
Chilkat.CreateCS ccs = new Chilkat.CreateCS();
Chilkat.CertStore certStore;
certStore = ccs.OpenCurrentUserStore();
Chilkat.Cert cert;
cert = certStore.FindCertBySubjectCN("Chilkat Software, Inc.");

if (cert == null ) {
    MessageBox.Show(cert.LastErrorText);
    return;
}

//  Our MIME object is currently empty.  Add some header fields
//  and a body:
mime.AddHeaderField("subject","this is a test");
mime.AddHeaderField("test123","this is a test 123");
mime.ContentType = "text/plain";
mime.Charset = "iso-8859-1";
mime.SetBodyFromPlainText("This is the body");

textBox1.Text += "Original MIME message:" + "\r\n";
textBox1.Refresh();
textBox1.Text += mime.GetMime() + "\r\n";
textBox1.Refresh();

//  The original MIME looks like this:
//  ----------------------------------
//  subject: this is a test
//  test123: this is a test 123
//  content-type: text/plain;
//  	 charset="iso-8859-1"
// 
//  This is the body
//  ----------------------------------

//  Add a detached signature.  Transfer the header fields
//  from our existing MIME to what will become the new outer
//  envelope.
bool transferHeaderFields;
transferHeaderFields = true;
success = mime.AddDetachedSignature2(cert,transferHeaderFields);
if (success != true) {
    MessageBox.Show(mime.LastErrorText);
    return;
}

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

MessageBox.Show("Success!");

//  The signed MIME looks like this:
//  --------------------------------
//  content-type: multipart/signed;
//  	boundary="----=_NextPart_e7c_2b68_282042d9.6ba23d56";
//  	protocol="application/x-pkcs7-signature";
//  	micalg=SHA1
//  subject: this is a test
//  test123: this is a test 123
// 
//  This is a multi-part message in MIME format.
// 
//  ------=_NextPart_e7c_2b68_282042d9.6ba23d56
//  content-type: text/plain;
//  	 charset="iso-8859-1"
// 
//  This is the body
//  ------=_NextPart_e7c_2b68_282042d9.6ba23d56
//  content-transfer-encoding: base64
//  content-type: application/x-pkcs7-signature;
//  	name="smime.p7s"
//  content-disposition: attachment;
//  	 filename="smime.p7s"
// 
//  MIIGAAYJKoZIhvcNAQcCoIIF8TCCBe0CAQExCzAJBgUrDgMCGgUAMAsGCSqGSIb3DQEHAaCC
//  A9kwggPVMIIDPqADAgECAhB4ouTcAmLszrGi170k1deSMA0GCSqGSIb3DQEBBQUAMFUxCzAJ
//  BgNVBAYTAlpBMSUwIwYDVQQKExxUaGF3dGUgQ29uc3VsdGluZyAoUHR5KSBMdGQuMR8wHQYD
//  VQQDExZUaGF3dGUgQ29kZSBTaWduaW5nIENBMB4XDTA3MDExNTAwMDAwMFoXDTA4MDExNTIz
//  NTk1OVowgZ0xCzAJBgNVBAYTAlVTMREwDwYDVQQIEwhJbGxpbm9pczEQMA4GA1UEBxMHV2hl
//  YXRvbjEfMB0GA1UEChMWQ2hpbGthdCBTb2Z0d2FyZSwgSW5jLjEnMCUGA1UECxMeU2VjdXJl
//  IEFwcGxpY2F0aW9uIERldmVsb3BtZW50MR8wHQYDVQQDExZDaGlsa2F0IFNvZnR3YXJlLCBJ
//  bmMuMIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAwR2t6b/Kn4VzNCOlj1YGkHxD
//  YPVnfZNIeO7hmutreK6kr94xm9RlQn+vkN1uRMhvSbOdds+B25o+AyAeuBmLsuxoNRCC9AUb
//  a37pY8eL04AaTEAm350tfnHGT44joSdFPoW5D91TDare6q5UaaccdEtXU4/LGqh+nHB9Idft
//  0S/rIpP2PK9TAwQ5V8dlMuBQQA+BUCg5MY9oqZgtnkX7O6OJSk8MT0lUhVg7EAge9iUx7Eu4
//  oWK88fkOo81pqHogTpGfy4nibWg72XkPk135leMw/Jme37q7OR/zm6HceFlyyO0WL1fYx09P
//  pYbj1lYNvVo8n38ohT8T/7h3N4GUlQIDAQABo4HYMIHVMAwGA1UdEwEB/wQCMAAwPgYDVR0f
//  BDcwNTAzoDGgL4YtaHR0cDovL2NybC50aGF3dGUuY29tL1RoYXd0ZUNvZGVTaWduaW5nQ0Eu
//  Y3JsMB8GA1UdJQQYMBYGCCsGAQUFBwMDBgorBgEEAYI3AgEWMB0GA1UdBAQWMBQwDjAMBgor
//  BgEEAYI3AgEWAwIHgDAyBggrBgEFBQcBAQQmMCQwIgYIKwYBBQUHMAGGFmh0dHA6Ly9vY3Nw
//  LnRoYXd0ZS5jb20wEQYJYIZIAYb4QgEBBAQDAgQQMA0GCSqGSIb3DQEBBQUAA4GBAAUMcxUb
//  eo5HTDKMaxMFFy3iA9i/ke4VLFw97yEG3raLTHZUlRwVxwLGLmW81dY/64nEDEgKi3Ifuohf
//  A0a3N3Ld7zwL1f/hdG2pQigLcvMymP9jj6DEQxOs03iADFguMpqkb79hbbURzsKX7pvWuNjQ
//  VGiowTuo1JXuSbsqaW7vMYIB7zCCAesCAQEwaTBVMQswCQYDVQQGEwJaQTElMCMGA1UEChMc
//  VGhhd3RlIENvbnN1bHRpbmcgKFB0eSkgTHRkLjEfMB0GA1UEAxMWVGhhd3RlIENvZGUgU2ln
//  bmluZyBDQQIQeKLk3AJi7M6xote9JNXXkjAJBgUrDgMCGgUAoF0wGAYJKoZIhvcNAQkDMQsG
//  CSqGSIb3DQEHATAcBgkqhkiG9w0BCQUxDxcNMDcwNDA0MTkzMDUyWjAjBgkqhkiG9w0BCQQx
//  FgQUevptGkutc0lb6gI3NPHovx4Di34wDQYJKoZIhvcNAQEBBQAEggEAk4jqKMsn7D+MjGtY
//  M9bnLdekBSxMVWPpKxk6hWg0NVOoiBOd/OOyH8FO/r7trmzr2Z9eJf1zpdjzpSPCwnGJzIy9
//  RunBBTJ+BxCbDXfjwJJTYVy1Uhsedv+o7Gfj9LlAVysNLjda5VcU7x/OOBVst034X+map3ds
//  85yBrfcJ/LyQs/lyZYmSPgOpFIBSy3oULPzYt45EUVsuk5qSZ1MA4HeIDW37b8OfQOW8pLEL
//  cBRducU19lpDOp5hBRZDR3zu+/9ddWKxKvcH04WitYRBi5TtqhQxpep+vRhJX8EPY6cgenJ+
//  lbDURg552YftF4EpDGALADR41j6sUMzb0QOz4A==
// 
//  ------=_NextPart_e7c_2b68_282042d9.6ba23d56--
// 
//