About RSA Public/Private Keys

Downloads for Windows/Linux and Install Instructions

require 'rubygems'
require 'chilkat'

cert = Chilkat::CkCert.new()

#  Load a digital certificate.
success = cert.LoadFromFile("digitalCert.cer")
if (success != true)
    print cert.lastErrorText() + "\n"
    exit
end

#  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:" + "\n";
print pubKey.getXml() + "\n";

#  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.new()

success = privKey.LoadRsaDerFile("PrivateKey.key")
if (success != true)
    print privKey.lastErrorText() + "\n"
    exit
end

#  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:" + "\n";
print privKey.getXml() + "\n";

rsa = Chilkat::CkRsa.new()
success = rsa.UnlockComponent("Anything for 30-day trial.")
if (success != true)
    print rsa.lastErrorText() + "\n"
    exit
end

#  You now realize that the private key really contains both
#  private and public parts.  Therefore, we may import the private
#  key and the choose to use either the public or private in our
#  encrypt/decrypt operations:
privKeyXml = privKey.getXml()
success = rsa.ImportPrivateKey(privKeyXml)
if (success != true)
    print rsa.lastErrorText() + "\n"
    exit
end