(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.

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

// 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.
BOOL success = [rsa GenerateKey: [NSNumber numberWithInt: 2048]];

// To 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);
NSLog(@"%@",rsa.LastErrorText);

// Now verify the signature:
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(@"%@",rsa.LastErrorText);
}

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

// Try it with the wrong hash algorithm:
success = [rsa VerifyStringENC: strData hashAlg: @"sha-1" sig: hexSig];
if (success == YES) {
    NSLog(@"%@",@"Signature verified!");
}
else {
    NSLog(@"%@",rsa.LastErrorText);
}