(Objective-C) JWE using ECDH-ES, BP-256, A256GCM

See more JSON Web Encryption (JWE) Examples

Create a JWE with the following header:

	{
	  "alg": "ECDH-ES",
	  "enc": "A256GCM",
	  "exp": 1621957030,
	  "cty": "NJWT",
	  "epk": {
	    "kty": "EC",
	    "x": "QLpJ_LpFx-6yJhsb4OvHwU1khLnviiOwYOvmf5clK7w"
	    "y": "AJh7pJ3zZKDJkm8rbeG69GBooTosXJgSsvNFH0i3Vxnu"
	    "crv": "BP-256"
	  }
	}

Note: This example requires Chilkat v9.5.0.87 or greater.

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

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

BOOL success;

// Load our brainpool BP-256 public key.

// 	{
// 	  "use": "enc",
// 	  "kid": "puk_idp_enc",
// 	  "kty": "EC",
// 	  "crv": "BP-256",
// 	  "x": "QLpJ_LpFx-6yJhsb4OvHwU1khLnviiOwYOvmf5clK7w",
// 	  "y": "AJh7pJ3zZKDJkm8rbeG69GBooTosXJgSsvNFH0i3Vxnu"
// 	}

CkoJsonObject *json = [[CkoJsonObject alloc] init];
[json UpdateString: @"use" value: @"enc"];
[json UpdateString: @"kid" value: @"puk_idp_enc"];
[json UpdateString: @"kty" value: @"EC"];
[json UpdateString: @"crv" value: @"BP-256"];
[json UpdateString: @"x" value: @"QLpJ_LpFx-6yJhsb4OvHwU1khLnviiOwYOvmf5clK7w"];
[json UpdateString: @"y" value: @"AJh7pJ3zZKDJkm8rbeG69GBooTosXJgSsvNFH0i3Vxnu"];

CkoPublicKey *pubkey = [[CkoPublicKey alloc] init];

success = [pubkey LoadFromString: [json Emit]];
if (success == NO) {
    NSLog(@"%@",pubkey.LastErrorText);
    return;
}

// Build our protected header:

// 	{
// 	  "alg": "ECDH-ES",
// 	  "enc": "A256GCM",
// 	  "exp": 1621957030,
// 	  "cty": "NJWT",
// 	  "epk": {
// 	    "kty": "EC",
// 	    "x": "QLpJ_LpFx-6yJhsb4OvHwU1khLnviiOwYOvmf5clK7w"
// 	    "y": "AJh7pJ3zZKDJkm8rbeG69GBooTosXJgSsvNFH0i3Vxnu"
// 	    "crv": "BP-256"
// 	  }
// 	}

// Use jwt only for getting the current date/time + 3600 seconds.
CkoJwt *jwt = [[CkoJwt alloc] init];

CkoJsonObject *jweProtHdr = [[CkoJsonObject alloc] init];
[jweProtHdr UpdateString: @"alg" value: @"ECDH-ES"];
[jweProtHdr UpdateString: @"enc" value: @"A256GCM"];
[jweProtHdr UpdateInt: @"exp" value: [jwt GenNumericDate: [NSNumber numberWithInt: 3600]]];
[jweProtHdr UpdateString: @"cty" value: @"NJWT"];
[jweProtHdr UpdateString: @"epk.kty" value: @"EC"];
[jweProtHdr UpdateString: @"epk.x" value: @"QLpJ_LpFx-6yJhsb4OvHwU1khLnviiOwYOvmf5clK7w"];
[jweProtHdr UpdateString: @"epk.y" value: @"AJh7pJ3zZKDJkm8rbeG69GBooTosXJgSsvNFH0i3Vxnu"];
[jweProtHdr UpdateString: @"epk.crv" value: @"BP-256"];

CkoJwe *jwe = [[CkoJwe alloc] init];
[jwe SetProtectedHeader: jweProtHdr];
[jwe SetPublicKey: [NSNumber numberWithInt: 0] pubKey: pubkey];

NSString *plainText = @"This is the text to be encrypted.";
NSString *strJwe = [jwe Encrypt: plainText charset: @"utf-8"];
if (jwe.LastMethodSuccess != YES) {
    NSLog(@"%@",jwe.LastErrorText);
    return;
}

NSLog(@"%@",strJwe);

NSLog(@"%@",@"Success.");