(Node.js) Get a Certificate's Key Size

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

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOS

var os = require('os');
if (os.platform() == 'win32') {  
  var chilkat = require('@chilkat/ck-node23-win64'); 
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node23-linux-arm');
    } else if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node23-linux-arm64');
    } else {
        var chilkat = require('@chilkat/ck-node23-linux-x64');
    }
} else if (os.platform() == 'darwin') {
  var chilkat = require('@chilkat/ck-node23-darwin-universal');
}

function chilkatExample() {

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

    var cert = new chilkat.Cert();
    success = cert.LoadFromBase64(sbCertBase64.GetAsString());
    if (success !== true) {
        console.log(cert.LastErrorText);
        return;
    }

    // Get the public key.
    // pubKey: PublicKey
    var pubKey = cert.ExportPublicKey();
    if (cert.LastMethodSuccess !== true) {
        console.log(cert.LastErrorText);
        return;
    }

    // In Chilkat version v9.5.0.67, the KeySize property was added.
    var numBits = pubKey.KeySize;
    console.log("Number of bits = " + numBits);

    // If using an older version of Chilkat, the key size can be obtained like this:
    var xml = new chilkat.Xml();
    xml.LoadXml(pubKey.GetXml());

    var binDat = new chilkat.BinData();
    binDat.AppendEncoded(xml.GetChildContent("Modulus"),"base64");

    numBits = 8 * binDat.NumBytes;
    console.log("Number of bits = " + numBits);


}

chilkatExample();