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

Demonstrates how to load an RSA 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: @"RSA"];
[json UpdateString: @"n" value: @"33TqqLR3eeUmDtHS89qF3p4MP7Wfqt2Zjj3lZjLjjCGDvwr9cJNlNDiuKboODgUiT4ZdPWbOiMAfDcDzlOxA04DDnEFGAf-kDQiNSe2ZtqC7bnIc8-KSG_qOGQIVaay4Ucr6ovDkykO5Hxn7OU7sJp9TP9H0JH8zMQA6YzijYH9LsupTerrY3U6zyihVEDXXOv08vBHk50BMFJbE9iwFwnxCsU5-UZUZYw87Uu0n4LPFS9BT8tUIvAfnRXIEWCha3KbFWmdZQZlyrFw0buUEf0YN3_Q0auBkdbDR_ES2PbgKTJdkjc_rEeM0TxvOUf7HuUNOhrtAVEN1D5uuxE1WSw"];
[json UpdateString: @"e" value: @"AQAB"];

// The JSON contains the following:
// { 
//   "kty": "RSA",
//   "n": "33TqqLR3eeUmDtHS89qF3p4MP7Wfqt2Zjj3lZjLjjCGDvwr9cJNlNDiuKboODgUiT4ZdPWbOiMAfDcDzlOxA04DDnEFGAf-kDQiNSe2ZtqC7bnIc8-KSG_qOGQIVaay4Ucr6ovDkykO5Hxn7OU7sJp9TP9H0JH8zMQA6YzijYH9LsupTerrY3U6zyihVEDXXOv08vBHk50BMFJbE9iwFwnxCsU5-UZUZYw87Uu0n4LPFS9BT8tUIvAfnRXIEWCha3KbFWmdZQZlyrFw0buUEf0YN3_Q0auBkdbDR_ES2PbgKTJdkjc_rEeM0TxvOUf7HuUNOhrtAVEN1D5uuxE1WSw",
//   "e": "AQAB",
// } 

// 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:
// <RSAPublicKey>
//     <Modulus>33TqqLR3eeUmDtHS89qF3p4MP7Wfqt2Zjj3lZjLjjCGDvwr9cJNlNDiuKboODgUiT4ZdPWbOiMAfDcDzlOxA04DDnEFGAf+kDQiNSe2ZtqC7bnIc8+KSG/qOGQIVaay4Ucr6ovDkykO5Hxn7OU7sJp9TP9H0JH8zMQA6YzijYH9LsupTerrY3U6zyihVEDXXOv08vBHk50BMFJbE9iwFwnxCsU5+UZUZYw87Uu0n4LPFS9BT8tUIvAfnRXIEWCha3KbFWmdZQZlyrFw0buUEf0YN3/Q0auBkdbDR/ES2PbgKTJdkjc/rEeM0TxvOUf7HuUNOhrtAVEN1D5uuxE1WSw==</Modulus>
//     <Exponent>AQAB</Exponent>
// </RSAPublicKey>

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

// PEM output
// -----BEGIN PUBLIC KEY-----
// MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA33TqqLR3eeUmDtHS89qF
// 3p4MP7Wfqt2Zjj3lZjLjjCGDvwr9cJNlNDiuKboODgUiT4ZdPWbOiMAfDcDzlOxA
// 04DDnEFGAf+kDQiNSe2ZtqC7bnIc8+KSG/qOGQIVaay4Ucr6ovDkykO5Hxn7OU7s
// Jp9TP9H0JH8zMQA6YzijYH9LsupTerrY3U6zyihVEDXXOv08vBHk50BMFJbE9iwF
// wnxCsU5+UZUZYw87Uu0n4LPFS9BT8tUIvAfnRXIEWCha3KbFWmdZQZlyrFw0buUE
// f0YN3/Q0auBkdbDR/ES2PbgKTJdkjc/rEeM0TxvOUf7HuUNOhrtAVEN1D5uuxE1W
// SwIDAQAB
// -----END PUBLIC KEY-----