(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 <C_CkStringBuilder.h>
#include <C_CkPrivateKey.h>
#include <C_CkJsonObject.h>
#include <C_CkJws.h>
#include <C_CkPublicKey.h>

void ChilkatSample(void)
    {
    HCkStringBuilder sbJwk;
    HCkPrivateKey eccKey;
    BOOL success;
    HCkJsonObject jwsProtHdr;
    HCkJws jws;
    int signatureIndex;
    BOOL bIncludeBom;
    const char *payloadStr;
    const char *jwsCompact;
    HCkJws jws2;
    HCkPublicKey eccPubKey;
    int v;
    HCkJsonObject joseHeader;

    // 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.
    sbJwk = CkStringBuilder_Create();
    CkStringBuilder_Append(sbJwk,"{\"kty\":\"EC\",");
    CkStringBuilder_Append(sbJwk,"\"crv\":\"P-521\",");
    CkStringBuilder_Append(sbJwk,"\"x\":\"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk\",");
    CkStringBuilder_Append(sbJwk,"\"y\":\"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2\",");
    CkStringBuilder_Append(sbJwk,"\"d\":\"AY5pb7A0UFiB3RELSD64fTLOSV_jazdF7fLYyuTw8lOfRhWg6Y6rUrPAxerEzgdRhajnu0ferB0d53vM9mE15j2C\"");
    CkStringBuilder_Append(sbJwk,"}");

    eccKey = CkPrivateKey_Create();
    // 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..)
    success = CkPrivateKey_LoadJwk(eccKey,CkStringBuilder_getAsString(sbJwk));
    if (success != TRUE) {
        printf("%s\n",CkPrivateKey_lastErrorText(eccKey));
        CkStringBuilder_Dispose(sbJwk);
        CkPrivateKey_Dispose(eccKey);
        return;
    }

    // Create the JWS Protected Header
    jwsProtHdr = CkJsonObject_Create();
    CkJsonObject_AppendString(jwsProtHdr,"alg","ES512");

    jws = CkJws_Create();

    // Set the protected header:
    signatureIndex = 0;
    CkJws_SetProtectedHeader(jws,signatureIndex,jwsProtHdr);

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

    // Set the payload.
    bIncludeBom = FALSE;
    payloadStr = "In our village, folks say God crumbles up the old moon into stars.";
    CkJws_SetPayload(jws,payloadStr,"utf-8",bIncludeBom);

    // Create the JWS
    // By default, the compact serialization is used.
    jwsCompact = CkJws_createJws(jws);
    if (CkJws_getLastMethodSuccess(jws) != TRUE) {
        printf("%s\n",CkJws_lastErrorText(jws));
        CkStringBuilder_Dispose(sbJwk);
        CkPrivateKey_Dispose(eccKey);
        CkJsonObject_Dispose(jwsProtHdr);
        CkJws_Dispose(jws);
        return;
    }

    printf("JWS: %s\n",jwsCompact);

    // 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.
    jws2 = CkJws_Create();

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

    eccPubKey = CkPrivateKey_GetPublicKey(eccKey);

    // Set the ECC public key used for validation.
    signatureIndex = 0;
    CkJws_SetPublicKey(jws2,signatureIndex,eccPubKey);
    CkPublicKey_Dispose(eccPubKey);

    // Validate the 1st (and only) signature at index 0..
    v = CkJws_Validate(jws2,signatureIndex);
    if (v < 0) {
        // Perhaps Chilkat was not unlocked or the trial expired..
        printf("Method call failed for some other reason.\n");
        printf("%s\n",CkJws_lastErrorText(jws2));
        CkStringBuilder_Dispose(sbJwk);
        CkPrivateKey_Dispose(eccKey);
        CkJsonObject_Dispose(jwsProtHdr);
        CkJws_Dispose(jws);
        CkJws_Dispose(jws2);
        return;
    }

    if (v == 0) {
        printf("Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.\n");
        CkStringBuilder_Dispose(sbJwk);
        CkPrivateKey_Dispose(eccKey);
        CkJsonObject_Dispose(jwsProtHdr);
        CkJws_Dispose(jws);
        CkJws_Dispose(jws2);
        return;
    }

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

    // Recover the original content:
    printf("%s\n",CkJws_getPayload(jws2,"utf-8"));

    // Examine the protected header:
    joseHeader = CkJws_GetProtectedHeader(jws2,signatureIndex);
    if (CkJws_getLastMethodSuccess(jws2) != TRUE) {
        printf("No protected header found at the given index.\n");
        CkStringBuilder_Dispose(sbJwk);
        CkPrivateKey_Dispose(eccKey);
        CkJsonObject_Dispose(jwsProtHdr);
        CkJws_Dispose(jws);
        CkJws_Dispose(jws2);
        return;
    }

    CkJsonObject_putEmitCompact(joseHeader,FALSE);

    printf("Protected (JOSE) header:\n");
    printf("%s\n",CkJsonObject_emit(joseHeader));
    CkJsonObject_Dispose(joseHeader);

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


    CkStringBuilder_Dispose(sbJwk);
    CkPrivateKey_Dispose(eccKey);
    CkJsonObject_Dispose(jwsProtHdr);
    CkJws_Dispose(jws);
    CkJws_Dispose(jws2);

    }