(C++) RSA Signature/Verify with .key and .cer

See more RSA Examples

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature.

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

void ChilkatSample(void)
    {
    // 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 .key file:
    bool success = privKey.LoadPemFile("privateKey.key");
    if (success != true) {
        std::cout << privKey.lastErrorText() << "\r\n";
        return;
    }

    const char *privKeyXml = 0;
    // Get the private key in XML format:
    privKeyXml = privKey.getXml();

    CkRsa rsa;

    // Import the private key into the RSA component:
    success = rsa.ImportPrivateKey(privKeyXml);
    if (success != true) {
        std::cout << rsa.lastErrorText() << "\r\n";
        return;
    }

    // Create the signature as a hex string:
    rsa.put_EncodingMode("hex");

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

    // Sign the string using the sha-1 hash algorithm.
    // Other valid choices are "md2", "sha256", "sha384",
    // "sha512", and "md5".
    const char *hexSig = rsa.signStringENC(strData,"sha-1");

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

    // Load a digital certificate from a .cer file:
    CkCert cert;

    success = cert.LoadFromFile("myCert.cer");
    if (success != true) {
        std::cout << cert.lastErrorText() << "\r\n";
        return;
    }

    CkPublicKey *pubKey = 0;

    pubKey = cert.ExportPublicKey();

    // Now verify using a separate instance of the RSA object:
    CkRsa rsa2;

    // Import the public key into the RSA object:
    success = rsa2.ImportPublicKey(pubKey->getXml());
    if (success != true) {
        std::cout << rsa2.lastErrorText() << "\r\n";
        return;
    }

    delete pubKey;

    // The signature is a hex string, so make sure the EncodingMode is correct:
    rsa2.put_EncodingMode("hex");

    // Verify the signature:
    success = rsa2.VerifyStringENC(strData,"sha-1",hexSig);
    if (success != true) {
        std::cout << rsa2.lastErrorText() << "\r\n";
        return;
    }

    std::cout << "Success." << "\r\n";
    }