(Unicode C++) RSA Sign with PKCS8 Encrypted Key

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it).

Note: This example requires Chilkat v11.0.0 or greater.

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#include <CkPrivateKeyW.h>
#include <CkRsaW.h>
#include <CkCertW.h>
#include <CkPublicKeyW.h>

void ChilkatSample(void)
    {
    bool success = false;

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

    CkPrivateKeyW privKey;

    // Load the private key from an RSA PEM file:
    success = privKey.LoadAnyFormatFile(L"raul_privateKey.key",L"a0123456789");
    if (success == false) {
        wprintf(L"%s\n",privKey.lastErrorText());
        return;
    }

    CkRsaW rsa;

    // Import the private key into the RSA component:
    success = rsa.UsePrivateKey(privKey);
    if (success == false) {
        wprintf(L"%s\n",rsa.lastErrorText());
        return;
    }

    // This example will sign a string, and receive the signature
    // in a hex-encoded string.  Therefore, set the encoding mode
    // to "hex":
    rsa.put_EncodingMode(L"hex");

    const wchar_t *strData = L"This is the string to be signed.";

    // Sign the string using the sha256 hash algorithm.
    // Other valid choices are sha1, sha384, sha512 and others.
    const wchar_t *hexSig = rsa.signStringENC(strData,L"sha256");
    if (rsa.get_LastMethodSuccess() == false) {
        wprintf(L"%s\n",rsa.lastErrorText());
        return;
    }

    wprintf(L"%s\n",hexSig);

    // Now verify with the public key.
    // This example shows how to use the public key from 
    // a digital certificate (.cer file)
    CkCertW cert;
    success = cert.LoadFromFile(L"raul_publicKey.cer");
    if (success == false) {
        wprintf(L"%s\n",cert.lastErrorText());
        return;
    }

    CkPublicKeyW pubKey;
    cert.GetPublicKey(pubKey);

    CkRsaW rsa2;
    success = rsa2.UsePublicKey(pubKey);
    if (success == false) {
        wprintf(L"%s\n",rsa2.lastErrorText());
        return;
    }

    // Verify the signature against the original data:
    rsa2.put_EncodingMode(L"hex");
    success = rsa2.VerifyStringENC(strData,L"sha256",hexSig);
    if (success == false) {
        wprintf(L"%s\n",rsa2.lastErrorText());
        return;
    }

    wprintf(L"Signature verified!\n");

    // Verify with incorrect data:
    success = rsa2.VerifyStringENC(L"something else",L"sha256",hexSig);
    if (success != true) {
        wprintf(L"Signature not verified! (which was expected in this case)\n");
    }
    else {
        wprintf(L"Hmmm... that's not right...\n");
    }
    }