(JavaScript) Get RSA Key Modulus from .cer or .key

Demonstrates how to get the RSA key modulus from either the certificate (.cer) or RSA key (.key). OpenSSL commands to do the same would be:

openssl x509 -inform DER -in "test.cer"  -modulus -noout 

openssl pkcs8 -inform DER -in​ "test.key"​ -outform PEM -passin pass:"12345​678a​"
   | openssl rsa -inform PEM -modulus -noout 

Note

This example is intended for running within a Chilkat.Js embedded JavaScript engine. All Chilkat JavaScript examples require Chilkat v11.4.0 or greater.

var success = false;

var privKey = new CkPrivateKey();

var password = "12345678a";
success = privKey.LoadPkcs8EncryptedFile("qa_data/certs/test_12345678a.key",password);
if (success == false) {
    console.log(privKey.LastErrorText);
    return;
}

var xml = new CkXml();
xml.LoadXml(privKey.GetXml());

// The XML contains the parts of the key in base64.
console.log("Private Key XML:");
console.log(xml.GetXml());

// We can get the base64 modulus like this:
var modulus = xml.GetChildContent("Modulus");
console.log("base64 modulus = " + modulus);

// To convert to hex:
var binDat = new CkBinData();
binDat.AppendEncoded(modulus,"base64");
var hexModulus = binDat.GetEncoded("hex");
console.log("hex modulus = " + hexModulus);

// Now get the modulus from the cert:
var cert = new CkCert();

success = cert.LoadFromFile("qa_data/certs/test_12345678a.cer");
if (success == false) {
    console.log(cert.LastErrorText);
    return;
}

// The cert contains the public key, which is composed of the
// modulus + exponent (for RSA keys).
var pubKey = new CkPublicKey();
cert.GetPublicKey(pubKey);

xml.LoadXml(pubKey.GetXml());
console.log("Public Key XML:");
console.log(xml.GetXml());

// Proceed in the same way as before....
modulus = xml.GetChildContent("Modulus");
console.log("base64 modulus = " + modulus);

// To convert to hex:
binDat.Clear();
binDat.AppendEncoded(modulus,"base64");
hexModulus = binDat.GetEncoded("hex");
console.log("hex modulus = " + hexModulus);