(Unicode C) Duplicate openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

Demonstrates how to duplicate this OpenSSL command:

openssl dgst -sha256 -verify pubKey.pem -signature signature.sig in.dat

1. Creates a SHA256 digest of the contents of the input file.
2. Verifies the SHA256 digest using the public key.

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#include <C_CkPublicKeyW.h>
#include <C_CkBinDataW.h>
#include <C_CkRsaW.h>

void ChilkatSample(void)
    {
    HCkPublicKeyW pubKey;
    BOOL success;
    HCkBinDataW bdFileData;
    HCkBinDataW bdSig;
    HCkRsaW rsa;

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

    pubKey = CkPublicKeyW_Create();

    // Load the public key from an PEM file:
    success = CkPublicKeyW_LoadFromFile(pubKey,L"pubKey.pem");
    if (success != TRUE) {
        wprintf(L"%s\n",CkPublicKeyW_lastErrorText(pubKey));
        CkPublicKeyW_Dispose(pubKey);
        return;
    }

    // Load the data of the original file that was signed.
    bdFileData = CkBinDataW_Create();
    success = CkBinDataW_LoadFile(bdFileData,L"in.dat");

    // Load the signature.
    bdSig = CkBinDataW_Create();
    success = CkBinDataW_LoadFile(bdSig,L"signature.sig");

    rsa = CkRsaW_Create();

    // Import the public key into the RSA component:
    success = CkRsaW_ImportPublicKeyObj(rsa,pubKey);
    if (success != TRUE) {
        wprintf(L"%s\n",CkRsaW_lastErrorText(rsa));
        CkPublicKeyW_Dispose(pubKey);
        CkBinDataW_Dispose(bdFileData);
        CkBinDataW_Dispose(bdSig);
        CkRsaW_Dispose(rsa);
        return;
    }

    // OpenSSL uses big-endian.
    CkRsaW_putLittleEndian(rsa,FALSE);

    success = CkRsaW_VerifyBd(rsa,bdFileData,L"sha256",bdSig);
    if (success != TRUE) {
        wprintf(L"%s\n",CkRsaW_lastErrorText(rsa));
        wprintf(L"The signature was invalid.\n");
        CkPublicKeyW_Dispose(pubKey);
        CkBinDataW_Dispose(bdFileData);
        CkBinDataW_Dispose(bdSig);
        CkRsaW_Dispose(rsa);
        return;
    }

    wprintf(L"The signature was verified.\n");


    CkPublicKeyW_Dispose(pubKey);
    CkBinDataW_Dispose(bdFileData);
    CkBinDataW_Dispose(bdSig);
    CkRsaW_Dispose(rsa);

    }