(Objective-C) Create JWS Using Private Key on a Smart Card

See more JSON Web Signatures (JWS) Examples

Note: This example requires Chilkat v11.5.0 or greater.

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#import <CkoCert.h>
#import <CkoJsonObject.h>
#import <CkoJws.h>
#import <NSString.h>
#import <CkoPublicKey.h>

BOOL success = NO;

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

// Load the certificate from a smart card.
CkoCert *cert = [[CkoCert alloc] init];

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

// Detect the connected smartcard or USB security token and load the default certificate.
success = [cert LoadFromSmartcard: @""];
if (success == NO) {
    NSLog(@"%@",cert.LastErrorText);
    return;
}

// Note: Chilkat provides many different ways to load a certificate from a smartcard or USB token,
// such as selecting a certificate if the card contains multiple certificates with private keys,
// or working with lower-level PKCS11 or ScMinidriver API's (both of which Chilkat provides).

// Create the JWS Protected Header
CkoJsonObject *jwsProtHdr = [[CkoJsonObject alloc] init];

if ([cert IsEcdsa] == YES) {
    [jwsProtHdr AppendString: @"alg" value: @"ES256"];
}
else {
    [jwsProtHdr AppendString: @"alg" value: @"RS256"];
}

CkoJws *jws = [[CkoJws alloc] init];

// Set the protected header:
int signatureIndex = 0;
[jws SetProtectedHeader: [NSNumber numberWithInt: signatureIndex] json: jwsProtHdr];

// Provide the private key via the certificate.
// This requires Chilkat v11.5.0 or greater.
[jws SetSigningCert: [NSNumber numberWithInt: signatureIndex] cert: cert];

// Set the payload.
BOOL bIncludeBom = NO;
NSString *payloadStr = @"In our village, folks say God crumbles up the old moon into stars.";
[jws SetPayload: payloadStr charset: @"utf-8" includeBom: bIncludeBom];

// Create the JWS
// By default, the compact serialization is used.
NSString *jwsCompact = [jws CreateJws];
if (jws.LastMethodSuccess == NO) {
    NSLog(@"%@",jws.LastErrorText);
    return;
}

NSLog(@"%@%@",@"JWS: ",jwsCompact);

// sample output:
// JWS: eyJhbGciOiJQUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.TRWhwRo5dMv9-8OzrInfJTwmUGYgjLfHk8lqF072ND-FmLWEBnUTOpY8oJXp8FdWw2SalbdOeNlrtlJjwk4XK8Ql2iJ_2qMCtxsvLPhKBOqFoAF4aBvTOEDVJDxf0DaBSiydEEtfTVV2iwBcjWabu5J2XieR5y7QZQtuHsn7T3qKBvCcCejN3Y2oqAT3qMHvu1fTms1r_91wBn_K7Wjd9UkZ1n02qQcUHJznR_OF2BgN7_KWIDAF9ZS9keoju2NPpPelO4yxa2XUPnehY3G7dHKoCxUEQR4d2Xc5voqDASTVCDqQS4PVOZdvT3Ein6-SanAlCwbWBbkvT8g6-5PImQ

// Now load the JWS, validate, and recover the original text.
CkoJws *jws2 = [[CkoJws alloc] init];

// Load the JWS.
success = [jws2 LoadJws: jwsCompact];

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

// Set the public key used for validation.
signatureIndex = 0;
[jws2 SetPublicKey: [NSNumber numberWithInt: signatureIndex] pubKey: pubKey];

// Validate the 1st (and only) signature at index 0..
int v = [[jws2 Validate: [NSNumber numberWithInt: signatureIndex]] intValue];
if (v < 0) {
    // Perhaps Chilkat was not unlocked or the trial expired..
    NSLog(@"%@",@"Method call failed for some other reason.");
    NSLog(@"%@",jws2.LastErrorText);
    return;
}

if (v == 0) {
    NSLog(@"%@",@"Invalid signature.  The key was incorrect, the JWS was invalid, or both.");
    return;
}

// If we get here, the signature was validated..
NSLog(@"%@",@"Signature validated.");

// Recover the original content:
NSLog(@"%@",[jws2 GetPayload: @"utf-8"]);

// Examine the protected header:

CkoJsonObject *joseHeader = [[CkoJsonObject alloc] init];
success = [jws2 GetProtectedH: [NSNumber numberWithInt: signatureIndex] json: joseHeader];
if (success == NO) {
    NSLog(@"%@",jws2.LastErrorText);
    return;
}

joseHeader.EmitCompact = NO;

NSLog(@"%@",@"Protected (JOSE) header:");
NSLog(@"%@",[joseHeader Emit]);

// Output:

// 	Signature validated.
// 	In our village, folks say God crumbles up the old moon into stars.
// 	Protected (JOSE) header:
// 	{ 
// 	  "alg": "RS256"
// 	}