(Visual FoxPro) About RSA Public/Private Keys

This example provides some additional information for understanding public/private key pairs. In demonstrates how a private key is a superset of the public key. A public key contains the modulus and exponent. The matching private key also contains the modulus and exponent, but also contains the additional private key parts.

Note: This example requires Chilkat v11.0.0 or greater.

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

LOCAL lnSuccess
LOCAL loCert
LOCAL loPubKey
LOCAL loPrivKey

lnSuccess = 0

loCert = CreateObject('Chilkat.Cert')

* Load a digital certificate.
lnSuccess = loCert.LoadFromFile("digitalCert.cer")
IF (lnSuccess = 0) THEN
    ? loCert.LastErrorText
    RELEASE loCert
    CANCEL
ENDIF

* A .cer file does not contain the private key.  It should contain
* the public key...
loPubKey = CreateObject('Chilkat.PublicKey')
loCert.GetPublicKey(loPubKey)

* Let's have a look at it (in XML format).
? "Public Key from Certificate:"
? loPubKey.GetXml()

* An RSA public key consists of a modulus and exponent.

* An RSA private key includes both the modulus and exponent,
* as well as other "big" numbers: P, Q, D, etc.

* Let's load an RSA private key from a DER-encoded file:
loPrivKey = CreateObject('Chilkat.PrivateKey')

lnSuccess = loPrivKey.LoadAnyFormatFile("PrivateKey.key","")
IF (lnSuccess <> 1) THEN
    ? loPrivKey.LastErrorText
    RELEASE loCert
    RELEASE loPubKey
    RELEASE loPrivKey
    CANCEL
ENDIF

* If this private key is the matching half to the public key from
* the certificate, then the modulus and exponent should
* be identical.  (Thus, a "private key" really contains both the public part as well as the private parts...).
? "Private Key from DER:"
? loPrivKey.GetXml()

RELEASE loCert
RELEASE loPubKey
RELEASE loPrivKey