def sign_message(payload, private_key)
      signature_urlencoded = ''

      key = OpenSSL::PKey::RSA.new(private_key)

      payload_decoded = CGI::unescape(payload.chomp('decode'))

      signature = key.sign(OpenSSL::Digest::MD5.new, payload_decoded)
      signature_base64 = Base64.strict_encode64(signature)
      signature_urlencoded = "#{CGI::escape(signature_base64)}decode"

      return signature_urlencoded
    end
def sign_message(payload, private_key)
      signature_urlencoded = ''

      key = OpenSSL::PKey::RSA.new(private_key)

      payload_decoded = CGI::unescape(payload.chomp('decode'))

      signature = key.sign(OpenSSL::Digest::MD5.new, payload_decoded)
      signature_base64 = Base64.strict_encode64(signature)
      signature_urlencoded = "#{CGI::escape(signature_base64)}decode"

      return signature_urlencoded
    end
Private: Sign a message using a private RSA key

 payload - The message to be signed
 private_key - An RSA private key

 Returns a base64-encoded and url-encoded hash of the $payload_string