(Objective-C) Encrypt File using X.509 Certificate using AES in CBC Mode

Demonstrates how to encrypt a file using an X.509 Certificate's public key, where the underlying bulk encryption algorithm is 128-bit AES in CBC mode. (The underlying bulk encryption algorithm can be specified to be other algorithms/strengths.)

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

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

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

// Use public-key cryptography for encryption.
crypt.CryptAlgorithm = @"pki";

// Get an X.509 certificate to use for encrypting.
// Note: Chilkat provides many different ways of loading a certificate, from many different formats,
// or if on Windows, from the installed certificates on the system.
// This example simply loads a certificate from a file.
// Also, for encryption, only the public key is needed.  Digital certificates embed the public key
// within the X.509 format itself.  Therefore, if you have a certificate, you also have the public key.
CkoCert *cert = [[CkoCert alloc] init];
BOOL success = [cert LoadFromFile: @"qa_data/certs/testCert.cer"];
if (success != YES) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

success = [crypt SetEncryptCert: cert];
if (success != YES) {
    NSLog(@"%@",crypt.LastErrorText);
    return;
}

// Indicate the underlying bulk encryption algorithm to be used:
crypt.Pkcs7CryptAlg = @"aes";
crypt.KeyLength = [NSNumber numberWithInt:128];

// Note: When doing public-key encryption the underlying bulk symmetric cipher mode will always be CBC. (at least with Chilkat...)

// There's one last option that could be set.  If is the RSA encryption encryption/padding scheme. 
// By default, RSAES_PKCS1-V1_5 is used.  If desired, the OaepPadding property could be set to YES to
// use RSAES_OAEP.  (We'll leave it set at the default value of NO)
crypt.OaepPadding = NO;

// Everything is specified.  Now just encrypt...
// The output is PKCS7 in binary DER format.
success = [crypt CkEncryptFile: @"qa_data/hamlet.xml" destFile: @"qa_output/hamlet.p7"];
if (success != YES) {
    NSLog(@"%@",crypt.LastErrorText);
    return;
}

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