Objective-C

Generate RSA Key and Sign a String

See more RSA Examples

Demonstrates how to generate a new RSA public/private key pair and use it to generate a signature for a string. The (binary) digital signature is returned as a hexidecimalized string. Objective-C

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

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

// Generate a 2048-bit RSA key.
CkoPrivateKey *privKey = [[CkoPrivateKey alloc] init];
success = [rsa GenKey: [NSNumber numberWithInt: 2048] privKey: privKey];

[rsa UsePrivateKey: privKey];

// Return the signature in hex.
rsa.EncodingMode = @"hex";

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

// Sign the SHA256 hash of the string.
NSString *hexSig = [rsa SignStringENC: strData hashAlg: @"sha256"];

NSLog(@"%@",hexSig);

// Now verify the signature:
CkoPublicKey *pubKey = [[CkoPublicKey alloc] init];
[privKey ToPublicKey: pubKey];
[rsa UsePublicKey: pubKey];

success = [rsa VerifyStringENC: strData hashAlg: @"sha256" sig: hexSig];
if (success == YES) {
    NSLog(@"%@",@"Signature verified!");
}
else {
    NSLog(@"%@",rsa.LastErrorText);
}

// Try it with an invalid signature:
success = [rsa VerifyStringENC: strData hashAlg: @"sha256" sig: @"not a valid sig"];
if (success == YES) {
    NSLog(@"%@",@"Signature verified!");
}
else {
    NSLog(@"%@",@"Signature validation failed!");
}

// Try it with invalid data:
success = [rsa VerifyStringENC: @"Not the original data" hashAlg: @"sha256" sig: hexSig];
if (success == YES) {
    NSLog(@"%@",@"Signature verified!");
}
else {
    NSLog(@"%@",@"Signature validation failed!");
}