# File lib/aws/core/authorize_v4.rb, line 47
      def authorization signer, datetime
        parts = []
        parts << "AWS4-HMAC-SHA256 Credential=#{access_key_id}/#{credential_string(datetime)}"
        parts << "SignedHeaders=#{signed_headers}"
        parts << "Signature=#{hex16(signature(signer, datetime))}"
        parts.join(', ')
      end