To guarantee secure communication, many maps-based key agreement protocols have been proposed. Due to inherent tamper-resistance, most of them are based on smart cards. Unfortunately, the cost of cards and readers makes these protocols costly. In the real world, common storage devices, such as universal serial bus (USB) thumb drives, portable HDDs, mobile phones, and laptop or desktop PCs, are widely used, and they are much cheaper or more convenient for storing user authentication information. These devices do not provide tamper-resistance; it is a challenge to design a secure authentication protocol using these kinds of memory devices. In this paper, we will propose a maps-based key agreement protocol without using smart cards. According to our analysis, the proposed protocol guarantees mutual authentication, and also resists different attacks. Therefore, our protocol is suitable even for practical applications.