Objective-C

RSA Signature/Verify with .key and .cer

See more RSA Examples

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature. Objective-C

#import <CkoPrivateKey.h>
#import <CkoRsa.h>
#import <NSString.h>
#import <CkoCert.h>
#import <CkoPublicKey.h>

BOOL success = NO;

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

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

//  Load the private key from an RSA .key file:
success = [privKey LoadPemFile: @"privateKey.key"];
if (success == NO) {
    NSLog(@"%@",privKey.LastErrorText);
    return;
}

CkoRsa *rsa = [[CkoRsa alloc] init];

//  Import the private key into the RSA component:
success = [rsa UsePrivateKey: privKey];
if (success == NO) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

//  Create the signature as a hex string:
rsa.EncodingMode = @"hex";

NSString *strData = @"This is the string to be signed.";

//  Sign the string using the sha256 hash algorithm.
//  Other valid choices are "md2", "sha1", "sha384",
//  "sha512", and "md5".
NSString *hexSig = [rsa SignStringENC: strData hashAlg: @"sha256"];

NSLog(@"%@",hexSig);

//  Load a digital certificate from a .cer file:
CkoCert *cert = [[CkoCert alloc] init];

success = [cert LoadFromFile: @"myCert.cer"];
if (success == NO) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

CkoPublicKey *pubKey = [[CkoPublicKey alloc] init];
[cert GetPublicKey: pubKey];

//  Now verify using a new instance of the RSA object:
CkoRsa *rsa2 = [[CkoRsa alloc] init];

//  Import the public key into the RSA object:
success = [rsa2 UsePublicKey: pubKey];
if (success == NO) {
    NSLog(@"%@",rsa2.LastErrorText);
    return;
}

//  The signature is a hex string, so make sure the EncodingMode is correct:
rsa2.EncodingMode = @"hex";

//  Verify the signature:
success = [rsa2 VerifyStringENC: strData hashAlg: @"sha256" sig: hexSig];
if (success == NO) {
    NSLog(@"%@",rsa2.LastErrorText);
    return;
}

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