def build_auth_sub_data(http_request, timestamp, nonce):
  """Creates the data string which must be RSA-signed in secure requests.

  For more details see the documenation on secure AuthSub requests:
  http://code.google.com/apis/accounts/docs/AuthSub.html#signingrequests

  Args:
    http_request: The request being made to the server. The Request's URL
        must be complete before this signature is calculated as any changes
        to the URL will invalidate the signature.
    nonce: str Random 64-bit, unsigned number encoded as an ASCII string in
        decimal format. The nonce/timestamp pair should always be unique to
        prevent replay attacks.
    timestamp: Integer representing the time the request is sent. The
        timestamp should be expressed in number of seconds after January 1,
        1970 00:00:00 GMT.
  """
  return '%s %s %s %s' % (http_request.method, str(http_request.uri),
                          str(timestamp), nonce)