(PureBasic) 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 PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkBinData.pb"
IncludeFile "CkXml.pb"
IncludeFile "CkPrivateKey.pb"
IncludeFile "CkPublicKey.pb"
IncludeFile "CkCert.pb"

Procedure ChilkatExample()

    privKey.i = CkPrivateKey::ckCreate()
    If privKey.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    password.s = "12345678a"
    success.i = CkPrivateKey::ckLoadPkcs8EncryptedFile(privKey,"qa_data/certs/test_12345678a.key",password)
    If success <> 1
        Debug CkPrivateKey::ckLastErrorText(privKey)
        CkPrivateKey::ckDispose(privKey)
        ProcedureReturn
    EndIf

    xml.i = CkXml::ckCreate()
    If xml.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkXml::ckLoadXml(xml,CkPrivateKey::ckGetXml(privKey))

    ; The XML contains the parts of the key in base64.
    Debug "Private Key XML:"
    Debug CkXml::ckGetXml(xml)

    ; We can get the base64 modulus like this:
    modulus.s = CkXml::ckGetChildContent(xml,"Modulus")
    Debug "base64 modulus = " + modulus

    ; To convert to hex:
    binDat.i = CkBinData::ckCreate()
    If binDat.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkBinData::ckAppendEncoded(binDat,modulus,"base64")
    hexModulus.s = CkBinData::ckGetEncoded(binDat,"hex")
    Debug "hex modulus = " + hexModulus

    ; Now get the modulus from the cert:
    cert.i = CkCert::ckCreate()
    If cert.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkCert::ckLoadFromFile(cert,"qa_data/certs/test_12345678a.cer")
    If success <> 1
        Debug CkCert::ckLastErrorText(cert)
        CkPrivateKey::ckDispose(privKey)
        CkXml::ckDispose(xml)
        CkBinData::ckDispose(binDat)
        CkCert::ckDispose(cert)
        ProcedureReturn
    EndIf

    ; The cert contains the public key, which is composed of the
    ; modulus + exponent (for RSA keys).
    pubKey.i = CkCert::ckExportPublicKey(cert)

    CkXml::ckLoadXml(xml,CkPublicKey::ckGetXml(pubKey))
    Debug "Public Key XML:"
    Debug CkXml::ckGetXml(xml)

    ; Proceed in the same way as before....
    modulus = CkXml::ckGetChildContent(xml,"Modulus")
    Debug "base64 modulus = " + modulus

    ; To convert to hex:
    CkBinData::ckClear(binDat)
    CkBinData::ckAppendEncoded(binDat,modulus,"base64")
    hexModulus = CkBinData::ckGetEncoded(binDat,"hex")
    Debug "hex modulus = " + hexModulus

    CkPublicKey::ckDispose(pubKey)



    CkPrivateKey::ckDispose(privKey)
    CkXml::ckDispose(xml)
    CkBinData::ckDispose(binDat)
    CkCert::ckDispose(cert)


    ProcedureReturn
EndProcedure