(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.

Chilkat C/C++ Library Downloads
MS Visual C/C++ Linux/CentOS C/C++ Alpine Linux C/C++ MAC OS X C/C++	armhf/aarch64 C/C++ C++ Builder iOS C/C++ Android C/C++	Solaris C/C++ MinGW C/C++

#include <CkEdDSA.h>
#include <CkPrng.h>
#include <CkPrivateKey.h>
#include <CkJsonObject.h>
#include <CkStringBuilder.h>

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

    CkEdDSA eddsa;
    CkPrng prng;
    CkPrivateKey privKey;

    // Generates a new ed25519 key and stores it in privKey.
    bool success = eddsa.GenEd25519Key(prng,privKey);
    if (success == false) {
        std::cout << eddsa.lastErrorText() << "\r\n";
        return;
    }

    // ----------------------------------------------------------
    // Ed25519 PKCS1 format
    // 
    // This is the format created by:  openssl genpkey -algorithm X25519 -out xkey.pem
    const char *pkcs1Base64 = privKey.getPkcs1ENC("base64");
    std::cout << pkcs1Base64 << "\r\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.
    const char *pkcs8Base64 = privKey.getPkcs8ENC("base64");
    std::cout << pkcs8Base64 << "\r\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.
    const char *password = "secret";
    const char *pkcs8EncBase64 = privKey.getPkcs8EncryptedENC("base64",password);
    std::cout << pkcs8EncBase64 << "\r\n";

    // ----------------------------------------------------------
    // Ed25519 in PEM format:
    // 
    const char *ed25519Pem = privKey.getPkcs1Pem();
    std::cout << ed25519Pem << "\r\n";

    // Sample output:

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

    // ----------------------------------------------------------
    // Ed25519 in JWK Format
    // 
    const char *jwk = privKey.getJwk();

    CkJsonObject json;
    json.Load(jwk);
    json.put_EmitCompact(false);
    std::cout << json.emit() << "\r\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
    // 
    const char *ed25519_xml = privKey.getXml();
    std::cout << ed25519_xml << "\r\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
    // 
    CkStringBuilder sbPubKeyHex;
    const char *privKeyHex = privKey.getRawHex(sbPubKeyHex);

    // We should have a 32-byte private key (a 64 character hex string).
    std::cout << "private key = " << privKeyHex << "\r\n";

    // We should have a 32-byte public key (a 64 character hex string).
    std::cout << "public key = " << sbPubKeyHex.getAsString() << "\r\n";

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