(Ruby) Get a Certificate's Key Size

Demonstrates how to get the RSA key size of a certificate (for example, 1024-bit, 2048-bit, etc.)

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

require 'chilkat'

#  For this example, I have a certificate in raw base64 format (not PEM),
#  that looks like this:  "MIIGkDCCBHigAwIBAgIUMDA ... s/iqLsLA=="
sbCertBase64 = Chilkat::CkStringBuilder.new()
success = sbCertBase64.LoadFile("qa_data/certs/base64Cert.txt","utf-8")

cert = Chilkat::CkCert.new()
success = cert.LoadFromBase64(sbCertBase64.getAsString())
if (success != true)
    print cert.lastErrorText() + "\n";
    exit
end

#  Get the public key.
# pubKey is a CkPublicKey
pubKey = cert.ExportPublicKey()
if (cert.get_LastMethodSuccess() != true)
    print cert.lastErrorText() + "\n";
    exit
end

#  In Chilkat version v9.5.0.67, the KeySize property was added.
numBits = pubKey.get_KeySize()
print "Number of bits = " + numBits.to_s() + "\n";

#  If using an older version of Chilkat, the key size can be obtained like this:
xml = Chilkat::CkXml.new()
xml.LoadXml(pubKey.getXml())

binDat = Chilkat::CkBinData.new()
binDat.AppendEncoded(xml.getChildContent("Modulus"),"base64")

numBits = 8 * binDat.get_NumBytes()
print "Number of bits = " + numBits.to_s() + "\n";