Objective-C

Create a JWS into a StringBuilder

See more JSON Web Signatures (JWS) Examples

Demonstrates Jws.CreateJwsSb, which creates a JWS and writes it into a StringBuilder.

Background. JWS (JSON Web Signature) integrity-protects a payload with a signature or MAC. The header alg names the algorithm; this example uses HMAC-SHA256 (HS256) with a symmetric MAC key.

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Objective-C

#import <CkoJws.h>
#import <CkoJsonObject.h>
#import <NSString.h>
#import <CkoStringBuilder.h>

BOOL success = NO;

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

//  Set the protected header for signer 0, specifying the signature algorithm (alg).
CkoJsonObject *header = [[CkoJsonObject alloc] init];
[header UpdateString: @"alg" value: @"HS256"];
success = [jws SetProtectedHeader: [NSNumber numberWithInt: 0] json: header];
if (success == NO) {
    NSLog(@"%@",jws.LastErrorText);
    return;
}

//  Set the payload to be signed.
BOOL bIncludeBom = NO;
success = [jws SetPayload: @"This is the content to sign." charset: @"utf-8" includeBom: bIncludeBom];
if (success == NO) {
    NSLog(@"%@",jws.LastErrorText);
    return;
}

//  Provide the HMAC key (base64) for signer 0.  In production, obtain the key from a secure source
//  rather than hard-coding it.
NSString *base64Key = @"YWJjZGVmZ2hpamtsbW5vcHFyc3R1dnd4eXowMTIzNDU=";
success = [jws SetMacKey: [NSNumber numberWithInt: 0] key: base64Key encoding: @"base64"];
if (success == NO) {
    NSLog(@"%@",jws.LastErrorText);
    return;
}

//  Create the JWS and write it into a StringBuilder.
CkoStringBuilder *sbJws = [[CkoStringBuilder alloc] init];
success = [jws CreateJwsSb: sbJws];
if (success == NO) {
    NSLog(@"%@",jws.LastErrorText);
    return;
}

NSLog(@"%@",[sbJws GetAsString]);