check for derivation of public key

gistfile1.txt

require 'base64'
require 'ecdsa'

sig01_key_base64 = {
    kty:"EC",
    kid:"11",
    crv:"P-256",
    x:"usWxHK2PmfnHKwXPS54m0kTcGJ90UiglWiGahtagnv8",
    y:"IBOL-C3BttVivg-lSreASjpkttcsz-1rb7btKLv8EX4",
    d:"V8kgd2ZBRuh2dgyVINBUqpPDr7BOMGcF22CQMIUHtNM"
}

private_key = ECDSA::Format::IntegerOctetString.decode(Base64.decode64(sig01_key_base64[:d]))

bx=ECDSA::Format::IntegerOctetString.decode(Base64.decode64(sig01_key_base64[:x]))
by=ECDSA::Format::IntegerOctetString.decode(Base64.decode64(sig01_key_base64[:y]))
group        = ECDSA::Group::Nistp256
sig01_pub_key= group.new_point([bx, by])

public_key  = group.generator.multiply_by_scalar(private_key)

puts "derived x: #{public_key.x} "
puts "       vs: #{sig01_pub_key.x}"
puts "derived y: #{public_key.y} "
puts "       vs: #{sig01_pub_key.y}"

2.3.0 :004 > load 'check1.rb'
derived x: 84479481090508879236361810314595438639920637850206250382769291656310074416895 
       vs: 84479481090508879236361810314595438639920637850206250382769291656310074416895
derived y: 14508547282523033594077281899984253063221771617900828323772342424228169781630 
       vs: 221382765198319077083920120796396551052321440967416757858684904626210296