C#

S/MIME Decrypt using Certificate and Private Key in Apple Keychain

See more Apple Keychain Examples

Decrypts S/MIME using a certificate with private key found in the Apple Keychain. C#

bool success = false;

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

//  Load the certificate to be used for decryption by the Subject Common Name
//  On MacOS and iOS, Chilkat will search the Keychain(s) for the matching certificate.
//  Note: The private key must be present to decrypt.
success = cert.LoadByCommonName("My Cert");
if (success == false) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

Debug.WriteLine("Cert has private key: " + Convert.ToString(cert.HasPrivateKey()));

//  Load the MIME to be decrypted.
//  We encrypted using this example:  S/MIME Encrypt using Certificate in Apple Keychain
Chilkat.Mime mime = new Chilkat.Mime();
success = mime.LoadMimeFile("./encrypted.mime");
if (success == false) {
    Debug.WriteLine(mime.LastErrorText);
    return;
}

Debug.WriteLine(mime.GetMime());
Debug.WriteLine("----");

//  Here's the encrypted MIME:

//  Subject: test
//  SomeHeader: 123
//  Content-Type: application/x-pkcs7-mime; name="smime.p7m"; smime-type="enveloped-data"
//  Content-Disposition: attachment; filename="smime.p7m"
//  Content-Transfer-Encoding: base64
//  
//  MIICSwYJKoZIhvcNAQcDoIICPDCCAjgCAQAxggGzMIIBrwIBADCBljCBgTELMAkGA1UEBhMCSVQx
//  EDAOBgNVBAgMB0JlcmdhbW8xGTAXBgNVBAcMEFBvbnRlIFNhbiBQaWV0cm8xFzAVBgNVBAoMDkFj
//  dGFsaXMgUy5wLkEuMSwwKgYDVQQDDCNBY3RhbGlzIENsaWVudCBBdXRoZW50aWNhdGlvbiBDQSBH
//  MwIQPCWvkSv8oQ7xRmEHJ6TzEDANBgkqhkiG9w0BAQEFAASCAQB3VZvHRE5EWxug7Sckpcz1ucDZ
//  YiTKiqmyPt75MhzNRQLtKFx/jWwlemUwnPMzeu6yutCkZ74Bdn7MBsfDqV3bUz43wAu+fRBteGvF
//  mTc00MfY8L7o8dkpj4AqAOCj4hKQzbSE99GvSzyXcPE2Gm5NrOPtKxqfFqbBRTCb4fBZP84LaL+x
//  rnYfrM4qXTppixyN8iFYCd4maEbMu/GA5o+j0BkDDnx42pILDoAGV/ERyx55Y3Nc2Mhm/cITBMNn
//  g7uS9KPrlYizNaqVu09Hi9jg4gdZaRiTjUqg05tSOk/YqIQxTgfscwSPY92/ewpI6e1EHtLt8Q33
//  gWCbERptSntUMHwGCSqGSIb3DQEHATAdBglghkgBZQMEAQIEENm1AxeXlEMx7p6McjHIj5CAUEQj
//  0GuJ5LnTqiqIjOiwmwNidl1N1TRluxX5vAQvwBuYE6bQK4+i04yn2Av3cucW4kvxgP2Nmni+XgQt
//  aPPKlasaVceEeZ15IYjw77/m3YYn

//  -------------------------------------
//  Decrypt the MIME.
success = mime.DecryptUsingCert(cert);
if (success == false) {
    Debug.WriteLine(mime.LastErrorText);
    return;
}

//  -------------------------------------
//  Note: A password dialog may be shown, possibly twice, when accessing the private key.
//  See the following blog post explaining how to suppress the dialog:
//  Suppress Password Dialog when Accessing Private Key in Apple Keychain

//  Show the unencrypted MIME
Debug.WriteLine(mime.GetMime());

//  Here's the decrypted MIME

//  Subject: test
//  SomeHeader: 123
//  Content-Type: text/plain
//  
//  This is the body.