(MFC) Get a Certificate's Key Size

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

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

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

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkCert cert;
    success = cert.LoadFromBase64(sbCertBase64.getAsString());
    if (success != true) {
        strOut.append(cert.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    //  Get the public key.
    CkPublicKey *pubKey = cert.ExportPublicKey();
    if (cert.get_LastMethodSuccess() != true) {
        strOut.append(cert.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    //  In Chilkat version v9.5.0.67, the KeySize property was added.
    int numBits = pubKey->get_KeySize();
    strOut.append("Number of bits = ");
    strOut.appendInt(numBits);
    strOut.append("\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();
    strOut.append("Number of bits = ");
    strOut.appendInt(numBits);
    strOut.append("\r\n");

    delete pubKey;


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }