Objective-C

JWE using "dir" Direct use of Shared Symmetric Key

See more JSON Web Encryption (JWE) Examples

Demonstrates how to create a JWE using the "dir" alg -- which is to directly use a shared symmetric key.

Note: This example requires Chilkat v9.5.0.66 or greater.

Objective-C

#import <NSString.h>
#import <CkoJwe.h>
#import <CkoJsonObject.h>

BOOL success = NO;

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

// Note: This example requires Chilkat v9.5.0.66 or greater.

NSString *plaintext = @"Live long and prosper.";

CkoJwe *jwe = [[CkoJwe alloc] init];

// First build the JWE Protected Header..
CkoJsonObject *jweProtHdr = [[CkoJsonObject alloc] init];
[jweProtHdr AppendString: @"alg" value: @"dir"];
[jweProtHdr AppendString: @"enc" value: @"A128GCM"];

// Don't forget to actually provide the protected header to the JWE object:
[jwe SetProtectedHeader: jweProtHdr];

// The JWE is to use 128-bit AES GCM encryption as specified by the "enc" parameter.
// Given that the "alg" = "dir", we are to directly specify the AES GCM key.
// (It is assumed that the decrypting side also has knowledge of the direct key to be used..)

// Our key will be these 16 hex bytes: 000102030405060708090A0B0C0D0E0F

// The SetWrappingKey method is also used for "dir" direct keys.
// However, if there are multiple recipients, they must all share the same CEK (Content Encryption Key),
// which is specified by calling SetWrappingKey with an index of 0.

int recipientIndex = 0;
[jwe SetWrappingKey: [NSNumber numberWithInt: recipientIndex] encodedKey: @"000102030405060708090A0B0C0D0E0F" encoding: @"hex"];

// Encrypt and return the JWE:
NSString *strJwe = [jwe Encrypt: plaintext charset: @"utf-8"];
if (jwe.LastMethodSuccess != YES) {
    NSLog(@"%@",jwe.LastErrorText);
    return;
}

// Show the JWE we just created:
NSLog(@"%@",strJwe);

// Decrypt the JWE.
CkoJwe *jwe2 = [[CkoJwe alloc] init];
success = [jwe2 LoadJwe: strJwe];
if (success != YES) {
    NSLog(@"%@",jwe2.LastErrorText);
    return;
}

[jwe2 SetWrappingKey: [NSNumber numberWithInt: 0] encodedKey: @"000102030405060708090A0B0C0D0E0F" encoding: @"hex"];

// Decrypt.
NSString *originalPlaintext = [jwe2 Decrypt: [NSNumber numberWithInt: 0] charset: @"utf-8"];
if (jwe2.LastMethodSuccess != YES) {
    NSLog(@"%@",jwe2.LastErrorText);
    return;
}

NSLog(@"%@",@"original text: ");
NSLog(@"%@",originalPlaintext);

// Sample output:
// eyJhbGciOiJkaXIiLCJlbmMiOiJBMTI4R0NNIn0..20HX5Huc7f1nQC4pBUtiCQ.axFZIxtZy5j0ifJQUzGXLKIpsBuxJA.eBrOC-NrsreN6JeGuOPk1g
// original text: 
// Live long and prosper.