(Visual FoxPro) 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 

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL loPrivKey
LOCAL lcPassword
LOCAL lnSuccess
LOCAL loXml
LOCAL lcModulus
LOCAL loBinDat
LOCAL lcHexModulus
LOCAL loCert
LOCAL loPubKey

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.PrivateKey')
loPrivKey = CreateObject('Chilkat.PrivateKey')

lcPassword = "12345678a"
lnSuccess = loPrivKey.LoadPkcs8EncryptedFile("qa_data/certs/test_12345678a.key",lcPassword)
IF (lnSuccess <> 1) THEN
    ? loPrivKey.LastErrorText
    RELEASE loPrivKey
    CANCEL
ENDIF

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Xml')
loXml = CreateObject('Chilkat.Xml')
loXml.LoadXml(loPrivKey.GetXml())

* The XML contains the parts of the key in base64.
? "Private Key XML:"
? loXml.GetXml()

* We can get the base64 modulus like this:
lcModulus = loXml.GetChildContent("Modulus")
? "base64 modulus = " + lcModulus

* To convert to hex:
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loBinDat = CreateObject('Chilkat.BinData')
loBinDat.AppendEncoded(lcModulus,"base64")
lcHexModulus = loBinDat.GetEncoded("hex")
? "hex modulus = " + lcHexModulus

* Now get the modulus from the cert:
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Cert')
loCert = CreateObject('Chilkat.Cert')

lnSuccess = loCert.LoadFromFile("qa_data/certs/test_12345678a.cer")
IF (lnSuccess <> 1) THEN
    ? loCert.LastErrorText
    RELEASE loPrivKey
    RELEASE loXml
    RELEASE loBinDat
    RELEASE loCert
    CANCEL
ENDIF

* The cert contains the public key, which is composed of the
* modulus + exponent (for RSA keys).
loPubKey = loCert.ExportPublicKey()

loXml.LoadXml(loPubKey.GetXml())
? "Public Key XML:"
? loXml.GetXml()

* Proceed in the same way as before....
lcModulus = loXml.GetChildContent("Modulus")
? "base64 modulus = " + lcModulus

* To convert to hex:
loBinDat.Clear()
loBinDat.AppendEncoded(lcModulus,"base64")
lcHexModulus = loBinDat.GetEncoded("hex")
? "hex modulus = " + lcHexModulus

RELEASE loPubKey

RELEASE loPrivKey
RELEASE loXml
RELEASE loBinDat
RELEASE loCert