RSA Signature/Verify with .key and .cer

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature.

Download Chilkat Ruby Library

require 'chilkat'

privKey = Chilkat::CkPrivateKey.new()

#  Load the private key from an RSA .key file:
success = privKey.LoadPemFile("privateKey.key")
if (success != true)
    print privKey.lastErrorText() + "\n"
    exit
end

#  Get the private key in XML format:
privKeyXml = privKey.getXml()

rsa = Chilkat::CkRsa.new()

#  Any string argument automatically begins the 30-day trial.
success = rsa.UnlockComponent("30-day trial")
if (success != true)
    print rsa.lastErrorText() + "\n"
    exit
end

#  Import the private key into the RSA component:
success = rsa.ImportPrivateKey(privKeyXml)
if (success != true)
    print rsa.lastErrorText() + "\n"
    exit
end

#  Create the signature as a hex string:
rsa.put_EncodingMode("hex")

strData = "This is the string to be signed."

#  Sign the string using the sha-1 hash algorithm.
#  Other valid choices are "md2" and "md5".
hexSig = rsa.signStringENC(strData,"sha-1")

print hexSig + "\n";

#  Load a digital certificate from a .cer file:
cert = Chilkat::CkCert.new()

success = cert.LoadFromFile("myCert.cer")
if (success != true)
    print cert.lastErrorText() + "\n"
    exit
end

# pubKey is a CkPublicKey
pubKey = cert.ExportPublicKey()

#  Now verify using a separate instance of the RSA object:
rsa2 = Chilkat::CkRsa.new()

#  Import the public key into the RSA object:
success = rsa2.ImportPublicKey(pubKey.getXml())
if (success != true)
    print rsa2.lastErrorText() + "\n"
    exit
end

#  The signature is a hex string, so make sure the EncodingMode is correct:
rsa2.put_EncodingMode("hex")

#  Verify the signature:
success = rsa2.VerifyStringENC(strData,"sha-1",hexSig)
if (success != true)
    print rsa2.lastErrorText() + "\n"
    exit
end

print "Success." + "\n"