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

Validates 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 <CkStringBuilderW.h>
#include <CkPublicKeyW.h>
#include <CkJwsW.h>
#include <CkJsonObjectW.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.

    // This example takes a JSON signature in compact serialization format,
    // and uses an ECDSA public key to validate and recover the protected header and payload.

    // We only need a public key for signature validation.  This is the ECDSA public key
    // that is used:

    //      {"kty":"EC", 
    //       "crv":"P-521", 
    //       "x":"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk", 
    //       "y":"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2" 
    //      } 

    CkStringBuilderW sbPubKey;
    sbPubKey.Append(L"{\"kty\":\"EC\",");
    sbPubKey.Append(L"\"crv\":\"P-521\",");
    sbPubKey.Append(L"\"x\":\"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk\",");
    sbPubKey.Append(L"\"y\":\"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2\"");
    sbPubKey.Append(L"}");

    CkPublicKeyW pubKey;
    bool success = pubKey.LoadFromString(sbPubKey.getAsString());
    if (success != true) {
        wprintf(L"%s\n",pubKey.lastErrorText());
        return;
    }

    CkJwsW jws;

    // Set the ECC public key:
    int signatureIndex = 0;
    jws.SetPublicKey(signatureIndex,pubKey);

    // Load the JWS.
    CkStringBuilderW sbJws;
    sbJws.Append(L"eyJhbGciOiJFUzUxMiJ9");
    sbJws.Append(L".");
    sbJws.Append(L"UGF5bG9hZA");
    sbJws.Append(L".");
    sbJws.Append(L"AdwMgeerwtHoh-l192l60hp9wAHZFVJbLfD_UxMi70cwnZOYaRI1bKPWROc-mZZq");
    sbJws.Append(L"wqT2SI-KGDKB34XO0aw_7XdtAG8GaSwFKdCAPZgoXD2YBJZCPEX3xKpRwcdOO8Kp");
    sbJws.Append(L"EHwJjyqOgzDO7iKvU8vcnwNrmxYbSW9ERBXukOXolLzeO_Jn");

    success = jws.LoadJwsSb(sbJws);
    if (success != true) {
        wprintf(L"%s\n",jws.lastErrorText());
        return;
    }

    // Validate the 1st (and only) signature at index 0..
    int v = jws.Validate(signatureIndex);
    if (v < 0) {
        // Perhaps Chilkat was not unlocked or the trial expired..
        wprintf(L"Method call failed for some other reason.\n");
        wprintf(L"%s\n",jws.lastErrorText());
        return;
    }

    if (v == 0) {
        wprintf(L"Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.\n");
        return;
    }

    // If we get here, the signature was validated..
    wprintf(L"Signature validated.\n");
    wprintf(L"--\n");

    // Recover the original content:
    wprintf(L"Recovered content:\n");
    wprintf(L"%s\n",jws.getPayload(L"utf-8"));
    wprintf(L"--\n");

    // Examine the protected header:
    CkJsonObjectW *joseHeader = jws.GetProtectedHeader(signatureIndex);
    if (jws.get_LastMethodSuccess() != true) {
        wprintf(L"No protected header found at the given index.\n");
        return;
    }

    joseHeader->put_EmitCompact(false);

    wprintf(L"Protected (JOSE) header:\n");
    wprintf(L"%s\n",joseHeader->emit());
    delete joseHeader;

    // Output:
    // (the string "Payload" was the content that was signed.)

    // 	Signature validated.
    // 	--
    // 	Recovered content:
    // 	Payload
    // 	--
    // 	Protected (JOSE) header:
    // 	{
    // 	  "alg": "ES512"
    // 	}
    }