class Google::Auth::ExternalAccount::AwsRequestSigner

def signature secret_access_key, date, string_to_sign, service
  k_date = hmac "AWS4#{secret_access_key}", date
  k_region = hmac k_date, @region_name
  k_service = hmac k_region, service
  k_credentials = hmac k_service, "aws4_request"
  hexhmac k_credentials, string_to_sign
end