(PHP Extension) 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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<?php

// The version number (9_5_0) should match version of the Chilkat extension used, omitting the micro-version number.
// For example, if using Chilkat v9.5.0.48, then include as shown here:
include("chilkat_9_5_0.php");

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

$eddsa = new CkEdDSA();
$prng = new CkPrng();
$privKey = new CkPrivateKey();

// Generates a new ed25519 key and stores it in privKey.
$success = $eddsa->GenEd25519Key($prng,$privKey);
if ($success == false) {
    print $eddsa->lastErrorText() . "\n";
    exit;
}

// ----------------------------------------------------------
// Ed25519 PKCS1 format
// 
// This is the format created by:  openssl genpkey -algorithm X25519 -out xkey.pem
$pkcs1Base64 = $privKey->getPkcs1ENC('base64');
print $pkcs1Base64 . "\n";

// 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.
$pkcs8Base64 = $privKey->getPkcs8ENC('base64');
print $pkcs8Base64 . "\n";

// 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.
$password = 'secret';
$pkcs8EncBase64 = $privKey->getPkcs8EncryptedENC('base64',$password);
print $pkcs8EncBase64 . "\n";

// ----------------------------------------------------------
// Ed25519 in PEM format:
// 
$ed25519Pem = $privKey->getPkcs1Pem();
print $ed25519Pem . "\n";

// Sample output:

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

// ----------------------------------------------------------
// Ed25519 in JWK Format
// 
$jwk = $privKey->getJwk();

$json = new CkJsonObject();
$json->Load($jwk);
$json->put_EmitCompact(false);
print $json->emit() . "\n";

// 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
// 
$ed25519_xml = $privKey->getXml();
print $ed25519_xml . "\n";

// 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
// 
$sbPubKeyHex = new CkStringBuilder();
$privKeyHex = $privKey->getRawHex($sbPubKeyHex);

// We should have a 32-byte private key (a 64 character hex string).
print 'private key = ' . $privKeyHex . "\n";

// We should have a 32-byte public key (a 64 character hex string).
print 'public key = ' . $sbPubKeyHex->getAsString() . "\n";

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

?>