(Objective-C) Load ECC Public Key from JWK Format (JSON Web Key)

Demonstrates how to load an ECC public key from JWK (JSON Web Key) format.

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

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

// Note: This example requires Chilkat v9.5.0.66 or later.
BOOL success;

// First build a JWK sample to load..
CkoJsonObject *json = [[CkoJsonObject alloc] init];
[json UpdateString: @"kty" value: @"EC"];
[json UpdateString: @"crv" value: @"P-256"];
[json UpdateString: @"x" value: @"oBUyo8CQAFPeYPvv78ylh5MwFZjTCLQeb042TjiMJxE"];
[json UpdateString: @"y" value: @"vvQyxZkUjJQUPU_0bCy3Pj5qQdfu8jwEfqEeYGZ95CU"];

// The JSON contains the following:
// { 
//   "kty": "EC",
//   "crv": "P-256",
//   "x": "oBUyo8CQAFPeYPvv78ylh5MwFZjTCLQeb042TjiMJxE",
//   "y": "vvQyxZkUjJQUPU_0bCy3Pj5qQdfu8jwEfqEeYGZ95CU",
// }

// Note: The JSON can contain other members, such as "use", "kid", or anything else.  These will be ignored.
json.EmitCompact = NO;

// Show the JWK string to be loaded:
NSString *jwkStr = [json Emit];

CkoPublicKey *pubKey = [[CkoPublicKey alloc] init];
// The LoadFromString method will automatically detect the format.
success = [pubKey LoadFromString: jwkStr];
if (success != YES) {
    NSLog(@"%@",pubKey.LastErrorText);
    return;
}

// OK.. the JWK is loaded.  It can be used in whatever way desired...

// The key can be retrieved in any other format, such as XML or PEM..
NSLog(@"%@",[pubKey GetXml]);

// XML output:
// <ECCPublicKey curve="secp256r1" 
//    x="A01532A3C0900053DE60FBEFEFCCA58793301598D308B41E6F4E364E388C2711" 
//    y="BEF432C599148C94143D4FF46C2CB73E3E6A41D7EEF23C047EA11E60667DE425">
//    MIIBSzCCAQMGByqGSM49AgEwgfcCAQEwLAYHKoZIzj0BAQIhAP////8AAAABAAAAAAAAAAAAAAAA////////////////MFsEIP////8AAAABAAAAAAAAAAAAAAAA///////////////8BCBaxjXYqjqT57PrvVV2mIa8ZR0GsMxTsPY7zjw+J9JgSwMVAMSdNgiG5wSTamZ44ROdJreBn36QBEEEaxfR8uEsQkf4vOblY6RA8ncDfYEt6zOg9KE5RdiYwpZP40Li/hp/m47n60p8D54WK84zV2sxXs7LtkBoN79R9QIhAP////8AAAAA//////////+85vqtpxeehPO5ysL8YyVRAgEBA0IABKAVMqPAkABT3mD77+/MpYeTMBWY0wi0Hm9ONk44jCcRvvQyxZkUjJQUPU/0bCy3Pj5qQdfu8jwEfqEeYGZ95CU=
// </ECCPublicKey>

// Choose PCKS1 or PCKS8 PEM format..
BOOL bPreferPkcs1 = NO;
NSLog(@"%@",[pubKey GetPem: bPreferPkcs1]);

// PEM output
// -----BEGIN PUBLIC KEY-----
// MIIBSzCCAQMGByqGSM49AgEwgfcCAQEwLAYHKoZIzj0BAQIhAP////8AAAABAAAA
// AAAAAAAAAAAA////////////////MFsEIP////8AAAABAAAAAAAAAAAAAAAA////
// ///////////8BCBaxjXYqjqT57PrvVV2mIa8ZR0GsMxTsPY7zjw+J9JgSwMVAMSd
// NgiG5wSTamZ44ROdJreBn36QBEEEaxfR8uEsQkf4vOblY6RA8ncDfYEt6zOg9KE5
// RdiYwpZP40Li/hp/m47n60p8D54WK84zV2sxXs7LtkBoN79R9QIhAP////8AAAAA
// //////////+85vqtpxeehPO5ysL8YyVRAgEBA0IABKAVMqPAkABT3mD77+/MpYeT
// MBWY0wi0Hm9ONk44jCcRvvQyxZkUjJQUPU/0bCy3Pj5qQdfu8jwEfqEeYGZ95CU=
// -----END PUBLIC KEY-----