Objective-C

JWE using AES Key Wrap and AES_128_CBC_HMAC_SHA_256

See more JSON Web Encryption (JWE) Examples

This example duplicates the example A.3 in RFC 7516 for JSON Web Encryption (JWE).

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

Objective-C

#import <NSString.h>
#import <CkoJwe.h>
#import <CkoJsonObject.h>
#import <CkoStringBuilder.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: {"alg":"A128KW","enc":"A128CBC-HS256"}
CkoJsonObject *jweProtHdr = [[CkoJsonObject alloc] init];
[jweProtHdr AppendString: @"alg" value: @"A128KW"];
[jweProtHdr AppendString: @"enc" value: @"A128CBC-HS256"];
[jwe SetProtectedHeader: jweProtHdr];

NSLog(@"%@%@",@"JWE Protected Header: ",[jweProtHdr Emit]);
NSLog(@"%@",@"--");

//  The example A.3 in RFC 7516 uses the following 128-bit AES key,
//  specified in JWK (JSON Web Key) format:
//       {"kty":"oct",
//        "k":"GawgguFyGrWKav7AX4VKUg"
//       }
//  This is just a way of saying: The key type ("kty") is 
//  a bunch of octets ("k") in base64url encoding.
//  We can simply set the AES wrapping key like this:
NSString *aesWrappingKey = @"GawgguFyGrWKav7AX4VKUg";
[jwe SetWrappingKey: [NSNumber numberWithInt: 0] encodedKey: aesWrappingKey encoding: @"base64url"];

//  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 that was just produced.
//  1) Load the JWE.
//  2) Set the AES wrapping key.
//  3) Decrypt.
CkoJwe *jwe2 = [[CkoJwe alloc] init];
success = [jwe2 LoadJwe: strJwe];
if (success != YES) {
    NSLog(@"%@",jwe2.LastErrorText);
    return;
}

//  Set the AES wrap key.
[jwe2 SetWrappingKey: [NSNumber numberWithInt: 0] encodedKey: aesWrappingKey encoding: @"base64url"];

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

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

//  ---------------------------------------------------------------------------------
//  It should also be possible to decrypt the JWE as shown in RFC 7516, Appendix A.3.7
//  because it was produced using the same AES Wrap key.

CkoStringBuilder *sbJwe = [[CkoStringBuilder alloc] init];
[sbJwe Append: @"eyJhbGciOiJBMTI4S1ciLCJlbmMiOiJBMTI4Q0JDLUhTMjU2In0."];
[sbJwe Append: @"6KB707dM9YTIgHtLvtgWQ8mKwboJW3of9locizkDTHzBC2IlrT1oOQ."];
[sbJwe Append: @"AxY8DCtDaGlsbGljb3RoZQ."];
[sbJwe Append: @"KDlTtXchhZTGufMYmOYGS4HffxPSUrfmqCHXaI9wOGY."];
[sbJwe Append: @"U0m_YmjN04DJvceFICbCVQ"];

success = [jwe2 LoadJweSb: sbJwe];
if (success != YES) {
    NSLog(@"%@",jwe2.LastErrorText);
    return;
}

[jwe2 SetWrappingKey: [NSNumber numberWithInt: 0] encodedKey: aesWrappingKey encoding: @"base64url"];

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

NSLog(@"%@",originalPlaintext);