An interoperability standard for certified mail systems Arne Tauber a, ⁎, Jörg Apitzsch b , 1 , Luca Boldrin c , 2 a Institute for Applied Information Processing and Communications, Graz University of Technology, Austria b Bremen online services GmbH, Am Fallturm 9, D-28359 Bremen, Germany c InfoCert S.p.a, C.so Stati Uniti, 14, I-35127 Padova, Italy abstract article info Article history: Received 2 January 2012 Accepted 9 March 2012 Available online 17 March 2012 Keywords: Certified electronic mail Registered electronic mail Interoperability Standard Security A large number of certified mail systems have been put into operation on the market over the last years. In contrast to standard mailing systems like e-Mail, certified mail systems provide the secure, reliable and evi- dential exchange of messages with the quality of traditional postal registered or certified mail. Most of these systems are tailored to national laws, policies, needs and technical requirements and are thus closed and only accessible by certain user groups. However, the ongoing globalization and opening of the markets, especially in the European Union, ask for global certified mailing as already known from e-Mail. Interoperability of cer- tified mail systems is a new and challenging research field. This article presents a framework and standard to make arbitrary certified mail systems interoperable. The presented approach uses a federated trust network of so-called electronic delivery gateways for seamless certified mailing across systems. This is achieved by converting protocols and system specifics on different layers using a harmonized interoperability protocol. The presented framework has been standardized by the European Telecommunications Standards Institute (ETSI) as Registered Electronic Mail specification for interoperable certified mail systems. © 2012 Elsevier B.V. All rights reserved. 1. Introduction People are accustomed to sending valuable documents in a secure and reliable way. This includes documents like deeds, contracts, bids, subpoenas, summons, etc. Regular mail has no security provisions and senders rely on the assumption of a correct and successful deliv- ery. This is where Registered Mail and Certified Mail come into play. Registered mail is a useful vehicle in the postal world for secure mail delivery by providing extended tracking possibilities. The certi- fied mail service provides the sender additional proofs of submission and receipt. Nowadays, more and more people are using electronic communica- tion means. However, standard communication systems like Internet electronic mail (e-Mail) have a poor evidential quality. They can rather be compared to sending a postcard, which lacks confidentiality, authen- ticity, integrity and non-repudiation. Extensions like S/MIME (Secure Multipurpose Mail Extensions) or PGP (Pretty Good Privacy) enhance the e-Mail protocol with additional cryptographic functionalities like confidentiality, integrity and authenticity. Nevertheless, the shortcom- ing of a non-repudiable fair exchange still remains. The Internet com- munity tried to address this issue by introducing the four receipting mechanisms of Message Disposition Notifications (MDN) specified by RFC 3798 [17], Delivery Status Notifications (DSN) specified by RFC 3461 [25], SMTP service extensions for message tracking specified by RFC 3885 [1] and signed S/MIME receipts specified by RFC 2634 [18]. Due to the open nature of Internet e-Mail, all these extensions rely on the assumption of a fairly acting recipient. This means the recipient actually returns a receipt after having received the message. Due to this gap, the research community has provided many pro- tocols for secure messaging over the last two decades. They have been published as fair non-repudiation protocols. The aim was to design security extensions for asynchronous communications providing sim- ilar added value as registered or certified mail do in the postal world. The terms certified mail systems (CMS) or certified electronic mailing (CEM) are used when applying such protocols in the context of elec- tronic mailing systems, for example Internet e-Mail. CEM is a quite young research discipline starting in the early 1990s. Due to an increasing demand by governments, postal operators and the industry, various CMS have been put into operation over the last five years. Popular examples of governmental systems are the Italian Posta Elettronica Certificata (PEC) [16], the Austrian Document Delivery System (DDS) for the public sector [34] and the German De-Mail system [7]. Particularly the justice sector relies on the secure and evidential document delivery and started to introduce such systems several years ago with the Austrian ERV (Elektronischer Rechtsverkehr) [31] or the German EGVP (Elektronisches Gerichts- und Verwaltungspostfach) [32], which is based on the Online Services Computer Interface (OSCI) standard [2]. In the private sector mainly postal operators, which are continuously shifting their postal services into the electronic world, have identified a gap in the market and provide certified electronic Computer Standards & Interfaces 34 (2012) 452–466 ⁎ Corresponding author. Tel.: + 43 316 8735533. E-mail addresses: Arne.Tauber@iaik.tugraz.at (A. Tauber), ja@bos-bremen.de (J. Apitzsch), Luca.Boldrin@infocert.it (L. Boldrin). 1 Tel.: +49 421 2049539. 2 Tel.: +39 49 8288093. 0920-5489/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.csi.2012.03.002 Contents lists available at SciVerse ScienceDirect Computer Standards & Interfaces journal homepage: www.elsevier.com/locate/csi