(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.

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

// 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:
BOOL success = [privKey LoadPemFile: @"privateKey.key"];
if (success != YES) {
    NSLog(@"%@",privKey.LastErrorText);
    return;
}

NSString *privKeyXml = 0;
// Get the private key in XML format:
privKeyXml = [privKey GetXml];

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

// Import the private key into the RSA component:
success = [rsa ImportPrivateKey: privKeyXml];
if (success != YES) {
    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 sha-1 hash algorithm.
// Other valid choices are "md2", "sha256", "sha384",
// "sha512", and "md5".
NSString *hexSig = [rsa SignStringENC: strData hashAlg: @"sha-1"];

NSLog(@"%@",hexSig);

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

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

CkoPublicKey *pubKey = 0;

pubKey = [cert ExportPublicKey];

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

// Import the public key into the RSA object:
success = [rsa2 ImportPublicKey: [pubKey GetXml]];
if (success != YES) {
    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: @"sha-1" sig: hexSig];
if (success != YES) {
    NSLog(@"%@",rsa2.LastErrorText);
    return;
}

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