Objective-C

RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

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Demonstrates how RSA sign the utf-8 byte representation of a string to get the signature in base64 format. Objective-C

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

BOOL success = NO;

// Assuming the smartcard/USB token is installed with the correct drivers from the manufacturer,
// this code can work on multiple platforms including Windows, MacOS, Linux, and iOS.

// Chilkat automatically detects and determines the way in which the HSM is used,
// which can be by PKCS11, Apple Keychain, Microsoft CNG / Crypto API, or ScMinidriver.

CkoCert *cert = [[CkoCert alloc] init];

// Set the token/smartcard PIN prior to loading.
cert.SmartCardPin = @"123456";

// Specify the certificate by its common name.
success = [cert LoadFromSmartcard: @"cn=chilkat-rsa-2048"];
if (success == NO) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

NSLog(@"%@%@",@"Signing with cert: ",cert.SubjectCN);

// Create a string to be hashed and signed.
CkoStringBuilder *sb = [[CkoStringBuilder alloc] init];
BOOL crlfLineEnding = YES;
int i;
for (i = 0; i <= 10; i++) {
    [sb AppendLine: @"This is a test." crlf: crlfLineEnding];
}

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

// Use the certificate's private key for signing.
success = [rsa SetX509Cert: cert usePrivateKey: YES];
if (success == NO) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

// Sign the SHA-256 hash of the utf-8 byte representation of the contents of sb
// Return the signature in base64 format.
rsa.EncodingMode = @"base64";
rsa.Charset = @"utf-8";
NSString *stringToSign = [sb GetAsString];
NSString *sigBase64 = [rsa SignStringENC: stringToSign hashAlg: @"sha256"];
if (rsa.LastMethodSuccess == NO) {
    NSLog(@"%@",rsa.LastErrorText);
    return;
}

NSLog(@"%@%@",@"RSA signature as base64: ",sigBase64);