(Objective-C) Convert RSA Private Key to Public Key

Demonstrates how to get a public RSA key from a private RSA key.

Note: This example requires Chilkat v11.0.0 or greater.

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#import <CkoPrivateKey.h>
#import <CkoPublicKey.h>

BOOL success = NO;

CkoPrivateKey *privKey = [[CkoPrivateKey alloc] init];

// Step 1: Load the private key from a source.
// (Chilkat can load private keys from all types of formats, and from in-memory bytes or encoded strings.
// see the online reference documentation for more options.)
success = [privKey LoadPemFile: @"qa_data/pem/VP_Private.pem"];
if (success == NO) {
    NSLog(@"%@",privKey.LastErrorText);
    return;
}

// Step 2: Get the public key object from the private key object.
CkoPublicKey *pubKey = [[CkoPublicKey alloc] init];
[privKey ToPublicKey: pubKey];

// Step 3: Save the public key in a desired format. 
// (Chilkat can load or save public and private keys in many different formats.  See
// the online reference documentation for more options.)

// Saves to a PKCS8 PEM file.
BOOL bPreferPkcs1 = NO;
success = [pubKey SavePemFile: bPreferPkcs1 path: @"qa_data/pem/VP_Public.pem"];
if (pubKey.LastMethodSuccess == NO) {
    NSLog(@"%@",pubKey.LastErrorText);
    return;
}

NSLog(@"%@",@"Extracted and saved public key from private key.");