(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 <CkPrivateKey.h>
#include <CkRsa.h>
#include <CkCert.h>
#include <CkPublicKey.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.

    CkPrivateKey privKey;

    // Load the private key from an RSA PEM file:
    success = privKey.LoadAnyFormatFile("raul_privateKey.key","a0123456789");
    if (success == false) {
        std::cout << privKey.lastErrorText() << "\r\n";
        return;
    }

    CkRsa rsa;

    // Import the private key into the RSA component:
    success = rsa.UsePrivateKey(privKey);
    if (success == false) {
        std::cout << rsa.lastErrorText() << "\r\n";
        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("hex");

    const char *strData = "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 char *hexSig = rsa.signStringENC(strData,"sha256");
    if (rsa.get_LastMethodSuccess() == false) {
        std::cout << rsa.lastErrorText() << "\r\n";
        return;
    }

    std::cout << hexSig << "\r\n";

    // Now verify with the public key.
    // This example shows how to use the public key from 
    // a digital certificate (.cer file)
    CkCert cert;
    success = cert.LoadFromFile("raul_publicKey.cer");
    if (success == false) {
        std::cout << cert.lastErrorText() << "\r\n";
        return;
    }

    CkPublicKey pubKey;
    cert.GetPublicKey(pubKey);

    CkRsa rsa2;
    success = rsa2.UsePublicKey(pubKey);
    if (success == false) {
        std::cout << rsa2.lastErrorText() << "\r\n";
        return;
    }

    // Verify the signature against the original data:
    rsa2.put_EncodingMode("hex");
    success = rsa2.VerifyStringENC(strData,"sha256",hexSig);
    if (success == false) {
        std::cout << rsa2.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Signature verified!" << "\r\n";

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