(CkPython) 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.

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import sys
import chilkat

cert = chilkat.CkCert()

# Load a digital certificate.
success = cert.LoadFromFile("digitalCert.cer")
if (success != True):
    print(cert.lastErrorText())
    sys.exit()

# A .cer file does not contain the private key.  It should contain
# the public key...
# pubKey is a CkPublicKey
pubKey = cert.ExportPublicKey()

# Let's have a look at it (in XML format).
print("Public Key from Certificate:")
print(pubKey.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:
privKey = chilkat.CkPrivateKey()

success = privKey.LoadAnyFormatFile("PrivateKey.key","")
if (success != True):
    print(privKey.lastErrorText())

    sys.exit()

# 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...).
print("Private Key from DER:")
print(privKey.getXml())