(Objective-C) Create PKCS7 (CMS) EnvelopedData

Encrypt some data to a recipient by creating a PKCS7 (CMS) EnvelopedData structure. The data will be encrypted using a symmetric content-encryption algorithm (e.g., AES), and the randomly generated symmetric key will be encrypted using the recipient’s RSA public key extracted from their X.509 certificate.

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#import <CkoCrypt2.h>
#import <CkoCert.h>
#import <NSString.h>

CkoCrypt2 *crypt = [[CkoCrypt2 alloc] init];

// Specify the encryption to be used.
// "pki" indicates "Public Key Infrastructure" and will create a PKCS7 encrypted (enveloped-data) message.
crypt.CryptAlgorithm = @"pki";
crypt.Pkcs7CryptAlg = @"aes";
crypt.KeyLength = [NSNumber numberWithInt:256];
crypt.OaepHash = @"sha256";
crypt.OaepPadding = YES;

CkoCert *cert = [[CkoCert alloc] init];

// Use a certificate found in the Windows certificate store.
BOOL success = [cert LoadByCommonName: @"My Certificate"];
if (success != YES) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

// Tell the crypt object to use the certificate.
[crypt SetEncryptCert: cert];

NSString *toBeEncrypted = @"This string is to be encrypted.";

// Get the result in multi-line BASE64 MIME format.
crypt.EncodingMode = @"base64_mime";
crypt.Charset = @"utf-8";

NSString *result = [crypt EncryptStringENC: toBeEncrypted];
if (success != YES) {
    NSLog(@"%@",crypt.LastErrorText);
    return;
}

// -------------------------------------------------------------------------
// See the following example to decrypt what was created in this example
// Decrypt PKCS7 (CMS) EnvelopedData
// -------------------------------------------------------------------------

NSLog(@"%@",result);

// Sample output:

// MIICSgYJKoZIhvcNAQcDoIICOzCCAjcCAQAxggHiMIIB3gIBADCBljCBgTELMAkGA1UEBhMCSVQx
// EDAOBgNVBAgMB0JlcmdhbW8xGTAXBgNVBAcMEFBvbnRlIFNhbiBQaWV0cm8xFzAVBgNVBAoMDkFj
// dGFsaXMgUy5wLkEuMSwwKgYDVQQDDCNBY3RhbGlzIENsaWVudCBBdXRoZW50aWNhdGlvbiBDQSBH
// MwIQPCWvkSv8oQ7xRmEHJ6TzEDA8BgkqhkiG9w0BAQcwL6APMA0GCWCGSAFlAwQCAQUAoRwwGgYJ
// KoZIhvcNAQEIMA0GCWCGSAFlAwQCAQUABIIBAKqHAPQNSsQoX7B2NH7QyEOWQRsSVs8oCHXmy8f4
// MVZD2er3bvYUCIomxpwbLEAl14qjUIMynahooYGgqip7+4FqL301G+BVjZVfEhHWj+VI1dAWnWuL
// VHlvc/pbQNBWqV8rKVJsNIsuAZkdj4WSwLVKxYkYX43B8fh/g71XN2DTJu7Z/824v48KBmgpQBOT
// 2q7IcDGxNPAFN2p6eavIVGn2LvhEbf/Fszyj+GR5tMcnQP1BOLJ3s3JzUBbvj8hcZrF1Vhl9HnTU
// YQx8G/KdW1mR+Wlhl3BWoK0LYKRTbnTx2BXOs0CY1SXOAdhKr01ZYjA+xW4nGzY0lfXS9QZjh9gw
// TAYJKoZIhvcNAQcBMB0GCWCGSAFlAwQBKgQQw0xTbfmnt0zjWHo5SaQIp4AgxTVY9E/Ncqy6t+RM
// 8y4c3Av62/wB8IpPUEmtM2OeuZo=