normalized     = normalize(params)
  canonicalized  = canonicalize(normalized)
  string_to_sign = "#{method}&#{encode('/')}&#{encode(canonicalized)}"
  key            = self.access_key_secret + '&'
  signature      = Base64.encode64(OpenSSL::HMAC.digest('sha1', key, string_to_sign)).strip
  normalized.push(['Signature', encode(signature)])