Lua Requires Chilkat v11.0.0+

About RSA Public/Private Keys

See more RSA Examples

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. Lua

local chilkat = require("chilkat")

local cert = chilkat.Cert.new()

-- Load a digital certificate.
local success = cert:load_from_file("digitalCert.cer")
if not success then
    print(cert.last_error_text)
    return
end

-- A .cer file does not contain the private key.  It should contain
-- the public key...
local pubKey = chilkat.PublicKey.new()
cert:get_public_key(pubKey)

-- Let's have a look at it (in XML format).
print("Public Key from Certificate:")
print(pubKey:get_xml())

-- 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:
local privKey = chilkat.PrivateKey.new()

success = privKey:load_any_format_file("PrivateKey.key", "")
if not success then
    print(privKey.last_error_text)
    return
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:")
print(privKey:get_xml())