(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.

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

LOCAL loCert
LOCAL lnSuccess
LOCAL loPubKey
LOCAL loPrivKey

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

* Load a digital certificate.
lnSuccess = loCert.LoadFromFile("digitalCert.cer")
IF (lnSuccess <> 1) THEN
    ? loCert.LastErrorText
    RELEASE loCert
    CANCEL
ENDIF

* A .cer file does not contain the private key.  It should contain
* the public key...
loPubKey = loCert.ExportPublicKey()

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

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

RELEASE loCert
RELEASE loPrivKey