More Secure IDSN Lines

As more companies switch to ISDN, security becomes the paramount concern.

Rainer Mauth

Is ISDN a secure communications medium just because it is digital? Though telecommunications carriers sometimes tend to give this impression, it is not. "ISDN can easily be intercepted by secret services or organized crime," says Andreas Pfitzmann, a professor and computer security expert at the University of Dresden in Germany.

Security risks include data, voice, and fax traffic. That's why Biodata (Lichtenfels), a small German hardware company, developed a new security device called Babylon , which addresses encryption of all media on Basic Rate Interface (BRI) and Primary Rate Interface (PRI) point-to-point ISDN links. It can sit anywhere between the n etwork terminator and the phone, PBX, or data terminal. Babylon encrypts the bit streams traversing the ISDN B-channels deploying a 112-bit DES-3 technique and a Rivest-Shamir-Adleman (RSA) algorithm for the exchange of keys.

Babylon works within a closed user group, but, like the PGP scheme on the Internet, it also works with public keys. Of course, for secure transmission, it requires a Babylon-compliant terminal on the other end. "We are working closely with Siemens, Bosch Telekom, and other major telecommunications equipment vendors to push Babylon to a de facto standard for secure and open communications on ISDN," says Tan Siekmann of Biodata. "If there is no Babylon device on the other end, the system warns you and passes the data over without encryption." This ensures that you can communicate with everyone without changing equipment.

Encryption is also moving into ISDN routers and PC Cards. "Security is definitely the next step in internetworking on ISDN," says Beat Brunner of Lightning Instrumentation (Lausanne), a network company. Manufacturers like Crypto AG (Zug, Switzerland) and KryptoKom (Aachen, Germany) echo his view. For example, Lightning's MultiCom series of ISDN routers now include a 128-bit International Data Encryption Algorithm (IDEA) encryption in software that works at the link level and the TCP/IP level.

Link encryption encodes all traffic, including packet headers, on a per-remote-site basis. It lets you build up, for example, a completely shielded intranet. IP-level encryption doesn't encrypt IP-header information and therefore allows for secure transmission over public IP networks such as the Internet.

To provide on-the-fly DES encryption and V.42 data compression on a PC Card Type II, Hypercope's (Aachen, Germany) new Hycard deploys a novel Hyperstone RISC digital-signal-processor (DSP) chip (see the article "RISC and DSP in One Architecture"). Says Annegret Neckermann of Hypercope, "Mobile workers are increasingly demanding se cure ISDN communications."

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Babylon Security

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Babylon enables secure voice, fax, and data transmission on ISDN.