(Ruby) Convert RSA Private Key to Public Key

Demonstrates how to get a public RSA key from a private RSA key.

Chilkat Ruby Downloads install from rubygems.org gem install chilkat or download... Ruby Library for Windows, MacOS, Linux, Alpine Linux

require 'chilkat'

key = Chilkat::CkPrivateKey.new()

# Step 1: Load the private key from a source.
# (Chilkat can load private keys from all types of formats, and from in-memory bytes or encoded strings.
# see the online reference documentation for more options.)
success = key.LoadPemFile("qa_data/pem/VP_Private.pem")
if (success != true)
    print key.lastErrorText() + "\n";
    exit
end

# Step 2: Get the public key object from the private key object.
# pubKey is a CkPublicKey
pubKey = key.GetPublicKey()
if (key.get_LastMethodSuccess() != true)
    print key.lastErrorText() + "\n";
    exit
end

# Step 3: Save the public key in a desired format. 
# (Chilkat can load or save public and private keys in many different formats.  See
# the online reference documentation for more options.)

# Saves to a PKCS8 PEM file.
bPreferPkcs1 = false
success = pubKey.SavePemFile(bPreferPkcs1,"qa_data/pem/VP_Public.pem")
if (pubKey.get_LastMethodSuccess() != true)
    print pubKey.lastErrorText() + "\n";
    exit
end

print "Extracted and saved public key from private key." + "\n";