(Objective-C) Get Ed25519 Key in Different Formats

Demonstrates how to get/save an Ed25519 private key to different formats.

Converting a private key from one format to another is done by loading in one format and saving/getting in another.

Note: This example requires Chilkat v9.5.0.83 or greater.

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#import <CkoEdDSA.h>
#import <CkoPrng.h>
#import <CkoPrivateKey.h>
#import <NSString.h>
#import <CkoJsonObject.h>
#import <CkoStringBuilder.h>

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

CkoEdDSA *eddsa = [[CkoEdDSA alloc] init];
CkoPrng *prng = [[CkoPrng alloc] init];
CkoPrivateKey *privKey = [[CkoPrivateKey alloc] init];

// Generates a new ed25519 key and stores it in privKey.
BOOL success = [eddsa GenEd25519Key: prng privKey: privKey];
if (success == NO) {
    NSLog(@"%@",eddsa.LastErrorText);
    return;
}

// ----------------------------------------------------------
// Ed25519 PKCS1 format
// 
// This is the format created by:  openssl genpkey -algorithm X25519 -out xkey.pem
NSString *pkcs1Base64 = [privKey GetPkcs1ENC: @"base64"];
NSLog(@"%@",pkcs1Base64);

// Sample output:  MC4CAQAwBQYDK2VuBCIEIB1mwirs+eC6XGbkjPIiZyBwQ7768uSd9v5PHOLFbIXo

// PKCS1 is a binary ASN.1 DER format.  You can examine the contents with two online tools:
// 1) Go to ASN.1 Decoder  and paste the base64 into the online form.
// 2) Or Decode Base64 ASN.1 to XML 

// The PKCS1 ASN.1 format for an Ed25519 key look like this:
//   SEQUENCE
//     INTEGER 0
//     SEQUENCE
//       OBJECT IDENTIFIER 1.3.101.110 curveX25519 (ECDH 25519 key agreement algorithm)
//     OCTET STRING 
//       OCTET STRING (32 byte) 1D66C...

// Save it directly to a file.
success = [privKey SavePkcs1File: @"qa_output/ed25519.key"];

// ----------------------------------------------------------
// Ed25519 Unencrypted PKCS8 format
// 
// For ed25519, the ASN.1 output is the same as for PKCS1.
NSString *pkcs8Base64 = [privKey GetPkcs8ENC: @"base64"];
NSLog(@"%@",pkcs8Base64);

// PKCS8 is a binary ASN.1 DER format.  You can examine the contents with two online tools:
// 1) Go to ASN.1 Decoder  and paste the base64 into the online form.
// 2) Or Decode Base64 ASN.1 to XML 

// ----------------------------------------------------------
// Ed25519 Encrypted PKCS8 format
// 
// Note: The encrypted output cannot be examined using the above online tools because the ASN.1 is encrypted.
NSString *password = @"secret";
NSString *pkcs8EncBase64 = [privKey GetPkcs8EncryptedENC: @"base64" password: password];
NSLog(@"%@",pkcs8EncBase64);

// ----------------------------------------------------------
// Ed25519 in PEM format:
// 
NSString *ed25519Pem = [privKey GetPkcs1Pem];
NSLog(@"%@",ed25519Pem);

// Sample output:

// -----BEGIN PRIVATE KEY-----
// MC4CAQAwBQYDK2VuBCIEIOKPhbULJagBAi7hbRdn1f4AAzh1RqqCHqCAvau7N6yO
// -----END PRIVATE KEY-----

// ----------------------------------------------------------
// Ed25519 in JWK Format
// 
NSString *jwk = [privKey GetJwk];

CkoJsonObject *json = [[CkoJsonObject alloc] init];
[json Load: jwk];
json.EmitCompact = NO;
NSLog(@"%@",[json Emit]);

// Sample output:
// {
//   "kty": "OKP",
//   "crv": "Ed25519",
//   "x": "SE2Kne5xt51z1eciMH2T2ftDQp96Gl6FhY6zSQujiP0",
//   "d": "O-eRXewadF0sNyB0U9omcnt8Qg2ZmeK3WSXPYgqe570",
//   "use": "sig"
// }

// In the above JWK, x is the public key, y is the private key.
// Both are 32 bytes and are base64-url encoded.

// ----------------------------------------------------------
// Ed25519 in XML Format
// 
NSString *ed25519_xml = [privKey GetXml];
NSLog(@"%@",ed25519_xml);

// Sample output:  <Ed25519KeyValue>w4b/gI0zgYKgjtfWLjNfc4issmP7Qap84uesYNgEefP/WoY3jNOhOzgTYsMtOnuyGn3MdA4NZtsUXVNI1NiTlA==</Ed25519KeyValue>

// The base64 content is composed of the concatenation of the 32-byte private key with the 32-byte public key and then base64 encoded.
// In other words:  Base64(privKey || pubKey)

// ----------------------------------------------------------
// Ed25519 in Raw Hex Format
// 
CkoStringBuilder *sbPubKeyHex = [[CkoStringBuilder alloc] init];
NSString *privKeyHex = [privKey GetRawHex: sbPubKeyHex];

// We should have a 32-byte private key (a 64 character hex string).
NSLog(@"%@%@",@"private key = ",privKeyHex);

// We should have a 32-byte public key (a 64 character hex string).
NSLog(@"%@%@",@"public key = ",[sbPubKeyHex GetAsString]);

// Sample output:
// key type = ed25519
// size in bits = 256
// private key = d4ee72dbf913584ad5b6d8f1f769f8ad3afe7c28cbf1d4fbe097a88f44755842
// public key = 19bf44096984cdfe8541bac167dc3b96c85086aa30b6b6cb0c5c38ad703166e1