(Objective-C) Send Encrypted Email using RSAES-OAEP with AES-128 CBC and SHA256

Demonstrates how to send encrypted email using RSAES-OAEP with SHA256 and AES-128 content encryption.

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

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#import <CkoCert.h>
#import <CkoEmail.h>
#import <CkoMailMan.h>

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

// Load an RSA-based certificate.
// (Encrypting an email only requires the public key.  Decrypting an email requires the private key.)
CkoCert *cert = [[CkoCert alloc] init];
BOOL success = [cert LoadFromFile: @"qa_data/rsaes-oaep/cert.pem"];
if (success != YES) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

CkoEmail *email = [[CkoEmail alloc] init];

// Create a simple email.
email.Subject = @"Sample RSAES-OAEP Encrypted Email";
email.Body = @"Sample RSAES-OAEP Encrypted Email";
email.From = @"support@chilkatsoft.com";

// Add a recipient.
// (The email is encrypted using the recipient's certificate.
// If sending to multiple recipients, then the AddEncryptCert method would
// need to be called once for each recipient's certificate.)
[email AddTo: @"Chilkat GMail" emailAddress: @"chilkat.support@gmail.com"];

// Set the email object properties to indicate the desired encryption.
email.Pkcs7CryptAlg = @"aes";
// If AES-256 is desired, set the following property to 256.
email.Pkcs7KeyLength = [NSNumber numberWithInt:128];
email.OaepPadding = YES;
// Other choices for the OAEP hash algorithm are "sha1", "sha384", and "sha512"
email.OaepHash = @"sha256";

// Provide the certificate to be used for encryption
[email AddEncryptCert: cert];

// Don't forget to indicate that the email should be encrypted when sent..
email.SendEncrypted = YES;

// The mailman object will do the RSAES-OAEP encryption when sending.
CkoMailMan *mailman = [[CkoMailMan alloc] init];

// 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 = [NSNumber numberWithInt:587];
mailman.StartTLS = YES;

// Send the email.  The mailman will encrypt the email as directed by the 
// property settings of the email object.
success = [mailman SendEmail: email];
if (success != YES) {
    NSLog(@"%@",mailman.LastErrorText);
    return;
}

success = [mailman CloseSmtpConnection];
if (success != YES) {
    NSLog(@"%@",@"Connection to SMTP server not closed cleanly.");
}

NSLog(@"%@",@"Mail Sent!");

// -----------------------------------------------------------
// This is an example of an RSAES-OAEP encrypted email
// -----------------------------------------------------------

// MIME-Version: 1.0
// Date: Thu, 27 Apr 2017 08:43:32 -0500
// Message-ID: <772DC039F0259C474BAC60240EA2BA2272402308@CHILKAT13>
// Content-Type: application/pkcs7-mime; name="smime.p7m"; smime-type="enveloped-data"
// Content-Transfer-Encoding: base64
// X-Priority: 3 (Normal)
// Subject: Sample RSAES-OAEP Encrypted Email
// From: support@chilkatsoft.com
// To: "Chilkat GMail" <chilkat.support@gmail.com>
// Content-Disposition: attachment; filename="smime.p7m"
// 
// MIICWQYJKoZIhvcNAQcDoIICSjCCAkYCAQAxggGgMIIBnAIBADB1MGgxCzAJBgNVBAYTAlVTMQsw
// CQYDVQQIDAJJTDEQMA4GA1UEBwwHV2hlYXRvbjEhMB8GA1UECgwYSW50ZXJuZXQgV2lkZ2l0cyBQ
// dHkgTHRkMRcwFQYDVQQDDA5DaGlsa2F0V2lkZ2V0cwIJAMRwugDmvniwMBwGCSqGSIb3DQEBBzAP
// oA0wCwYJYIZIAWUDBAIBBIIBABr0E1dKJjK0FAYRz/NCtJmBeB0nUxgcuBnhGPI/UeyGub3cCo+K
// G5F4/iVTBJqVvYIF5+fvBnyTginwv7OiUiFWLyihiFC3NIyZJO22+XMHpNatCffTPZk10WswkTgk
// G3ApnRvGQAaldnFD0Hs8drPU4vBvY9QsjT7YDGa6u2NMX+sr1ewEZArqU0mNfJ6RsEYd5FQbFEVF
// qLmnz8Dt+yhoJlUtfUd8TXIeqHRJ7RxKOTSzlBZaAdTv2QX4oL9IcAgZeTg5iw+yRPkSAwWyg+I/
// 7fybLsUpRGDHTGUU+AvHvP0kYKa1mkvccBVEC/+4hEyhpS1tWIR5ByY6vM76Z+8wgZwGCSqGSIb3
// DQEHATAdBglghkgBZQMEAQIEEKqD0YDHX1NsVDaV32UczpeAcLteQyRPTV4hATjwcPiVelPfeWNs
// xZKRGaEBqLM8+Y+V4ciCFoOlgJuOcP4m1PTHyilfzd+SCsKz5l1C7+sfPf36n2aacX6IWga59Bz5
// QbWrOHDUT7O5PnGwKVgQFw3Cj4GrdPGWKcoqxB0HuKnj3WA=