(C++) Get a Certificate's Key Size

Demonstrates how to get the RSA key size of a certificate (for example, 1024-bit, 2048-bit, etc.)

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

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#include <CkStringBuilder.h>
#include <CkCert.h>
#include <CkPublicKey.h>
#include <CkXml.h>
#include <CkBinData.h>

void ChilkatSample(void)
    {
    bool success = false;

    // For this example, I have a certificate in raw base64 format (not PEM),
    // that looks like this:  "MIIGkDCCBHigAwIBAgIUMDA ... s/iqLsLA=="
    CkStringBuilder sbCertBase64;
    success = sbCertBase64.LoadFile("qa_data/certs/base64Cert.txt","utf-8");

    CkCert cert;
    success = cert.LoadFromBase64(sbCertBase64.getAsString());
    if (success == false) {
        std::cout << cert.lastErrorText() << "\r\n";
        return;
    }

    // Get the public key.
    CkPublicKey pubKey;
    cert.GetPublicKey(pubKey);

    int numBits = pubKey.get_KeySize();
    std::cout << "Number of bits = " << numBits << "\r\n";

    // If using an older version of Chilkat, the key size can be obtained like this:
    CkXml xml;
    xml.LoadXml(pubKey.getXml());

    CkBinData binDat;
    binDat.AppendEncoded(xml.getChildContent("Modulus"),"base64");

    numBits = 8 * binDat.get_NumBytes();
    std::cout << "Number of bits = " << numBits << "\r\n";
    }