(Objective-C) Encrypt MIME using RSAES-OAEP with SHA256 and AES-128 content encryption

Demonstrates how to encrypt MIME 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 <CkoMime.h>
#import <CkoStringBuilder.h>
#import <CkoCert.h>

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

BOOL success;
CkoMime *mime = [[CkoMime alloc] init];

// Create a MIME message to encrypt.
[mime NewMultipartMixed];
[mime AddHeaderField: @"someHeader1" value: @"Some value 1"];
[mime AddHeaderField: @"someHeader2" value: @"Some value 2"];

CkoMime *part0 = [[CkoMime alloc] init];
[part0 AddHeaderField: @"hdrA" value: @"Some value A"];
[part0 AddHeaderField: @"hdrB" value: @"Some value B"];
part0.ContentType = @"text/plain";
[part0 SetBody: @"This is the plain-text body."];

CkoMime *part1 = [[CkoMime alloc] init];
[part1 AddHeaderField: @"hdrX" value: @"Some value X"];
[part1 AddHeaderField: @"hdrY" value: @"Some value Y"];
part1.ContentType = @"text/xml";
[part1 SetBody: @"<a>This is the XML body</a>"];

[mime AppendPart: part0];
[mime AppendPart: part1];

// The MIME to be encrypted:
CkoStringBuilder *sbMime = [[CkoStringBuilder alloc] init];
[mime GetMimeSb: sbMime];
NSLog(@"%@",[sbMime GetAsString]);

// 	Content-Type: multipart/mixed; boundary="------------080303020600020604010008"
// 	someHeader1: Some value 1
// 	someHeader2: Some value 2
// 
// 	--------------080303020600020604010008
// 	hdrA: Some value A
// 	hdrB: Some value B
// 	Content-Type: text/plain
// 
// 	This is the plain-text body.
// 	--------------080303020600020604010008
// 	hdrX: Some value X
// 	hdrY: Some value Y
// 	Content-Type: text/xml
// 
// 	<a>This is the XML body</a>
// 	--------------080303020600020604010008--
// 

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

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

// Encrypt the MIME (to create S/MIME, which stands for "Secure MIME")
success = [mime Encrypt: cert];
if (success != YES) {
    NSLog(@"%@",mime.LastErrorText);
    return;
}

NSLog(@"%@",@"---------------");
NSLog(@"%@",@"Encrypted MIME:");
NSLog(@"%@",@"---------------");
NSLog(@"%@",[mime GetMime]);

NSLog(@"%@",@"Success.");

// ---------------------------------------------------
// This is sample output for RSAES-OAEP encrypted MIME:
// ---------------------------------------------------

// Content-Type: application/x-pkcs7-mime; name="smime.p7m"; smime-type="enveloped-data"
// someHeader1: Some value 1
// someHeader2: Some value 2
// Content-Disposition: attachment; filename="smime.p7m"
// Content-Transfer-Encoding: base64
// 
// MIIDvAYJKoZIhvcNAQcDoIIDrTCCA6kCAQAxggGgMIIBnAIBADB1MGgxCzAJBgNVBAYTAlVTMQsw
// CQYDVQQIDAJJTDEQMA4GA1UEBwwHV2hlYXRvbjEhMB8GA1UECgwYSW50ZXJuZXQgV2lkZ2l0cyBQ
// dHkgTHRkMRcwFQYDVQQDDA5DaGlsa2F0V2lkZ2V0cwIJAMRwugDmvniwMBwGCSqGSIb3DQEBBzAP
// oA0wCwYJYIZIAWUDBAIBBIIBAFaUL1ga1bOrdqYKcMm+FHUacBvzfBxk0fnPA0AMBdN8BvTWT3CN
// YuqBhjOGyq0FpYD9pVZybUuFMCVsVyIW2O62HnsOK58YaPEUUcdH2sI+yjqX9UAn0P0nVDSsVdeK
// W8x9kMfZg+3UP+y1q+lu7VRJO3f2C9oLQpTkc4VW4n7UOcUI0waykLCjCTL8lFDb7/J3GeuMKyhH
// 5riNz50kpbzqn7m2Ks9yA+QmcTdXclclGFr2vwEUFzSdT2pxh/vaUrogCxkYWbQ2eV7vZg6O4kV0
// aqHBqySkPTAzHKiHH8K8GVdlTuJ8350CpICa4T8w7/Ht5I7dyOPPKy4C+rVtrvcwggH+BgkqhkiG
// 9w0BBwEwHQYJYIZIAWUDBAECBBDTC2WNBN+z2I47/4Feu9YqgIIB0MZvl3nC/q/Wzil6HtfQTr12
// Q5moHY+ORzAa1P9XvX2ZUFhW530mV395mQw/A4o4ekmX9eRPEZquYzZPLT8hNeZIuNdhpcSQUmad
// rKnKkR0wKJ3jJ3LhOIohVBQSYs8kVDZKq6lJBIznlsurFelZoNEhyRschhteDZx5rb7fCe8c2+/O
// DHxaqaHCAzm/Bd7kcg6FFfuTZy3tu0PgP5IsXN4OFA3kkvwjAs4XsVS8jdIcmDNBkYieE8WmJOIm
// Mz7mh/CHWLgWfGKa0Dkb9RcbFgLwYNT3GzuXFw9XPbKkEZjEAtJajWbN6P0WQl96YYd9qZxUpGxZ
// zjTHEYzViUdUXolfpLufttrRXyxN1RFWhNFMFbv66xYqklMSgpdM/Mbk+EuvX6eXayDPvDBpfYMw
// NoRAzv1Ony2c0ez9rBemJICicxAzpuvHbRxdjYs63Dnv+TYgpBK12AxWWpPIjXvw0WQKgTC3Tg8s
// EnuGhpENqso/clJBEBSn4+2WhYtYbdI5sVme67lvqQl1Xxy3r18SWaQbyDOwgYi1E+54lMDOxMy0
// y0FPHk5pP45DnXWj+XORPp5LhuZr5mf62YOXSSUwR5P0cXy4Rc+pN5lhRQPCf5z2