Generate HMAC in Ruby

gen_hmac.rb

require 'digest'
require 'base64'
require 'cgi'
require 'time'
require 'openssl'
require 'json'

SHARED_SECRET = 'sup3rs3cr3t!!'

def signString(string_to_sign, shared_secret)
	return OpenSSL::HMAC.digest('sha512', shared_secret, string_to_sign)
end

payload = {
	:name => 'joe smith',
	:category => 'people',
	:action => 'transport',
	:where => 'pluto',
	:timestamp => Time.now.to_i.to_s
}

json_payload = JSON.generate(payload)
signature = signString(json_payload, SHARED_SECRET)

encoded_signature = Base64.urlsafe_encode64(signature)
encoded_payload = Base64.urlsafe_encode64(json_payload)

puts "/?data=#{encoded_payload}&signature=#{encoded_signature}"