(C++) Create a JWS Using ECDSA P-521 SHA-512

Creates and verifies a JSON Web Signature (JWS) that uses ECDSA P-521 SHA-512

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

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#include <CkStringBuilder.h>
#include <CkPrivateKey.h>
#include <CkJsonObject.h>
#include <CkJws.h>
#include <CkPublicKey.h>

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

    // Note: This example requires Chilkat v9.5.0.66 or greater.

    // Use the following ECC key loaded from JWK format.
    CkStringBuilder sbJwk;
    sbJwk.Append("{\"kty\":\"EC\",");
    sbJwk.Append("\"crv\":\"P-521\",");
    sbJwk.Append("\"x\":\"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk\",");
    sbJwk.Append("\"y\":\"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2\",");
    sbJwk.Append("\"d\":\"AY5pb7A0UFiB3RELSD64fTLOSV_jazdF7fLYyuTw8lOfRhWg6Y6rUrPAxerEzgdRhajnu0ferB0d53vM9mE15j2C\"");
    sbJwk.Append("}");

    CkPrivateKey eccKey;
    // Note: This example loads the ECDSA key from JWK format.  Any format can be loaded
    // into the private key object. (See the online reference documentation..)
    bool success = eccKey.LoadJwk(sbJwk.getAsString());
    if (success != true) {
        std::cout << eccKey.lastErrorText() << "\r\n";
        return;
    }

    // Create the JWS Protected Header
    CkJsonObject jwsProtHdr;
    jwsProtHdr.AppendString("alg","ES512");

    CkJws jws;

    // Set the protected header:
    int signatureIndex = 0;
    jws.SetProtectedHeader(signatureIndex,jwsProtHdr);

    // Set the ECC key:
    jws.SetPrivateKey(signatureIndex,eccKey);

    // Set the payload.
    bool bIncludeBom = false;
    const char *payloadStr = "In our village, folks say God crumbles up the old moon into stars.";
    jws.SetPayload(payloadStr,"utf-8",bIncludeBom);

    // Create the JWS
    // By default, the compact serialization is used.
    const char *jwsCompact = jws.createJws();
    if (jws.get_LastMethodSuccess() != true) {
        std::cout << jws.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "JWS: " << jwsCompact << "\r\n";

    // Note: ECC signatures use random values, so the output will be different each time a signature is produced.
    // sample output:
    // JWS: eyJhbGciOiJFUzUxMiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.AFOnOtZ8UTp-ed1PfLfXxwGU7zT_jnmGGxew-d1CP6SfKa5RUhav5mF4szhSof22JaoQ742VIa0eZ0s1rhBnj8y6APr6g6vKzIpYZlJsnjzjUwAjDQOLmcsjxrrRfATh-NEv7G0Z9FrjdJasS44tCG2EnG6aT2TW-sPG0dy5o9jUWCzi

    // Now load the JWS, validate, and recover the original text.
    CkJws jws2;

    // Load the JWS.
    success = jws2.LoadJws(jwsCompact);

    CkPublicKey *eccPubKey = eccKey.GetPublicKey();

    // Set the ECC public key used for validation.
    signatureIndex = 0;
    jws2.SetPublicKey(signatureIndex,*eccPubKey);
    delete eccPubKey;

    // Validate the 1st (and only) signature at index 0..
    int v = jws2.Validate(signatureIndex);
    if (v < 0) {
        // Perhaps Chilkat was not unlocked or the trial expired..
        std::cout << "Method call failed for some other reason." << "\r\n";
        std::cout << jws2.lastErrorText() << "\r\n";
        return;
    }

    if (v == 0) {
        std::cout << "Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both." << "\r\n";
        return;
    }

    // If we get here, the signature was validated..
    std::cout << "Signature validated." << "\r\n";

    // Recover the original content:
    std::cout << jws2.getPayload("utf-8") << "\r\n";

    // Examine the protected header:
    CkJsonObject *joseHeader = jws2.GetProtectedHeader(signatureIndex);
    if (jws2.get_LastMethodSuccess() != true) {
        std::cout << "No protected header found at the given index." << "\r\n";
        return;
    }

    joseHeader->put_EmitCompact(false);

    std::cout << "Protected (JOSE) header:" << "\r\n";
    std::cout << joseHeader->emit() << "\r\n";
    delete joseHeader;

    // Output:
    // 	Signature validated.
    // 	In our village, folks say God crumbles up the old moon into stars.
    // 	Protected (JOSE) header:
    // 	{
    // 	  "alg": "ES512"
    // 	}
    }