How to extract key-pair from a certificate in Xcode

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Objective-C

Hi
I'm building an iOS app which requires use of certificate.
I've used the following function to extract the identity from the certificate (which i've added into my app bundle).

(SecIdentityRef)getClientCertificate
 {
    NSString *thePath = [[NSBundle mainBundle] pathForResource:@"Certificates" ofType:@"p12"];
    if(!thePath)
    {
        NSLog(@"NULL");
        return NULL;
    }
    NSData *PKCS12Data = [[NSData alloc] initWithContentsOfFile:thePath] ;
    CFDataRef inPKCS12Data = (CFDataRef)CFBridgingRetain(PKCS12Data);
    CFStringRef password = CFSTR("********");
    const void *keys[] = { kSecImportExportPassphrase };
    const void *values[] = { password };
    CFDictionaryRef optionsDictionary = CFDictionaryCreate(NULL, keys, values, 1, NULL, NULL);
    CFArrayRef items = CFArrayCreate(NULL, 0, 0, NULL);
    OSStatus ret = SecPKCS12Import(inPKCS12Data, optionsDictionary, &items);
    if (ret != errSecSuccess)
    {
        // TODO: handle error.
        NSLog(@"-> SecPKCS12Import error (%d)", (int)ret);
    }
    CFRelease(optionsDictionary);
    
    CFDictionaryRef identityDict = CFArrayGetValueAtIndex(items, 0);
    SecIdentityRef identityApp = nil;
    if(!identityDict)
        return nil;
    identityApp = (SecIdentityRef)CFDictionaryGetValue(identityDict, kSecImportItemIdentity);
    
    SecIdentityRef      identity;
    SecCertificateRef   cert;
    OSStatus            err;
    CFStringRef         certName;
    
    identity = identityApp;
    assert( (identity != NULL) && (CFGetTypeID(identity) == SecIdentityGetTypeID()) );
    cert = NULL;
    err = SecIdentityCopyCertificate(identity, &cert);
    assert(err == noErr);
    assert(cert != NULL);
    
    certName = SecCertificateCopySubjectSummary(cert);
    assert(certName != NULL);
    
    NSLog(@"%@" , (id) CFBridgingRelease(certName));
    //NSDictionary *userInfo = [NSDictionary dictionaryWithObjectsAndKeys:(id)CFBridgingRelease(certName),@"USERID",nil];
    
    [[NSNotificationCenter defaultCenter] postNotificationName:@"UserInfoReceived" object:nil];
    
    //CFRelease(cert);
    //CFRelease(certName);
    return identityApp;
}

I've also used the following function to get information from the certificate.

-(NSString *)copySummaryString:(SecIdentityRef) identity

{
    
    // Get the certificate from the identity.
    
    SecCertificateRef myReturnedCertificate = NULL;
    
    OSStatus status = SecIdentityCopyCertificate (identity,
                                                  
                                                  &myReturnedCertificate);  // 1
    
    
    
    if (status) {
        
        NSLog(@"SecIdentityCopyCertificate failed.\n");
        
        return NULL;
        
    }
    
    
    
    CFStringRef certSummary = SecCertificateCopySubjectSummary
    
    (myReturnedCertificate);  // 2
    NSString* summaryString = [[NSString alloc] initWithString:(__bridge NSString *)certSummary];//3
    CFRelease(certSummary);
    return summaryString;   
}

Now i need to extract the public/private key pair from the certificate, i've searched a lot and i even read the "Certificate, Key, and Trust Services Programming Guide", and i've found some functions that generates a key pair for use on the mobile device. But i want the key-pair of the my certificate (the one which i've retrieved from the above function).

how can i do this?

Best Regards.