(Unicode C++) Create ECSDA Signature using Raw r and s Format (not ASN.1)

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Demonstrates how to create an ECDSA signature using the raw r/s format.

ECDSA signatures have two equal sized parts, r and s. There are two common formats for encoding the signature:

(a) Concatenating the raw byte array of r and s
(b) Encoding both into a structured ASN.1 / DER sequence.

This example demonstrates how to create a signature that is a byte array of r and s concatenated.

Note: This example requires Chilkat v9.5.0.97 or greater.

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#include <CkStringBuilderW.h>
#include <CkPrivateKeyW.h>
#include <CkPrngW.h>
#include <CkEccW.h>
#include <CkPublicKeyW.h>

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

    // To create an ECDSA signature, the data first needs to be hashed.  Then the hash
    // is signed.

    CkStringBuilderW sb;
    sb.Append(L"The quick brown fox jumps over the lazy dog");
    const wchar_t *hash = sb.getHash(L"sha256",L"base64",L"utf-8");

    // Load the ECDSA key to be used for signing.
    CkPrivateKeyW privKey;
    bool success = privKey.LoadPemFile(L"qa_data/ecc/secp256r1-key-pkcs8.pem");
    if (success != true) {
        wprintf(L"%s\n",privKey.lastErrorText());
        return;
    }

    CkPrngW prng;
    CkEccW ecdsa;

    // Produce a signature that is not ASN.1, but is instead the concatenation
    // of the raw r and s signature parts.
    // This feature was added in Chilkat v9.5.0.97
    ecdsa.put_AsnFormat(false);

    const wchar_t *ecdsaSigBase64 = ecdsa.signHashENC(hash,L"base64",privKey,prng);
    if (ecdsa.get_LastMethodSuccess() != true) {
        wprintf(L"%s\n",ecdsa.lastErrorText());
        return;
    }

    wprintf(L"ECDSA signature = %s\n",ecdsaSigBase64);

    // -----------------------------------------------------------
    // Now let's verify the signature using the public key.

    CkPublicKeyW pubKey;
    success = pubKey.LoadFromFile(L"qa_data/ecc/secp256r1-pubkey.pem");
    if (success != true) {
        wprintf(L"%s\n",pubKey.lastErrorText());
        return;
    }

    // Note: When verifying, Chilkat will auto-detect the format for both kinds of ECDSA signatures (ASN.1 or binary r+s)
    int result = ecdsa.VerifyHashENC(hash,ecdsaSigBase64,L"base64",pubKey);
    if (result == 1) {
        wprintf(L"Signature is valid.\n");
        return;
    }

    if (result == 0) {
        wprintf(L"Signature is invalid.\n");
        return;
    }

    if (result < 0) {
        wprintf(L"%s\n",ecdsa.lastErrorText());
        wprintf(L"The VerifyHashENC method call failed.\n");
        return;
    }
    }