Balancing Act

CALEA isn't just about providing law-enforcement agencies with information about calls. It's also about finding viable, cost-effective ways to provide only the information that they're legally entitled to.

CALEA gives U.S. law-enforcement agencies the right to monitor ("wiretap") telephone calls handled by wireless and landline providers. The bulk of the legislation isn't controversial. The devil is in the details, and the wireless industry is caught in the middle of a tug-of-war between personal privacy, effective crime-fighting and cost-effectiveness.

The telecom standard that can be used to provide compliance with CALEA is J-STD-025, which currently comes in two flavors, J-STD-025 and J-STD-025 Revision A, and may eventually come in a third to handle packet-data issues. The use of the standard is voluntary, but widespread implementations can be expected because it will be considered "safe harbor," a legal term that means that implementing the standard will be considered conformance with the legislation.

When lawfully authorized electronic surveillance is discussed, most people envision a scene from a movie with agents wearing earphones listening to a nasty criminal from within a parked, windowless van. Although this does occur, much monitoring doesn't include listening to the conversation at all. It's usually more efficient just to find out whom the subject was talking to and when rather than filtering through hours of tape-recorded and largely irrelevant conversations. It's this more mundane part of surveillance that's the most controversial.

In traditional landline systems, the information associated with a phone call is simple, straightforward and easily interpreted. The calling and called parties' phone numbers likely will be available — with one of them being the subject of the order — along with the call's time and duration. The callers' locations can be determined precisely from the phone numbers. With advanced services, such as conference calling and call waiting, and with wireless communications, the amount of information available is greater but is less easily interpreted. Telecom legislation also has grown around historical landline concepts, which aren't always translatable to wireless without ambiguity. And with ambiguity, you can be sure that civil-liberties organizations, law enforcement and telecom providers all will have different interpretations.

J-STD-025
The telecom industry's first try at addressing CALEA was in a joint TIA/ATIS standard J-STD-025, published in December 1997. It addressed what the industry thought were the law's requirements, but law enforcement strongly disagreed. To emphasize their dislike for this proposal, about 35 law-enforcement agencies each submitted the 70-page FBI ballot comments with their own cover letters attached. The controversial items became known as the "punch list," which was referred to the FCC for a decision. When it came, it was a solid jab to the industry because it ruled that most of the punch list should be implemented.

The industry had no choice but to implement the punch list as quickly as possible. Implementation was in early 2000 and included a variety of new messages in the protocol to handle the additional requirements. One new capability is notifying law enforcement whenever parties in a conference call or other multiparty call are added to the call, dropped from the call or placed on hold. This ability enables them to pinpoint who was talking to whom and when.

If a call is being recorded, any caller-dialed DTMF digits can be obtained easily. However, law-enforcement representatives argued successfully that even if they weren't recording the call, these should be sent to them. It's unclear that this argument makes any sense because obtaining this information is difficult, and interpreting it is even more difficult. Systems will vary in their tolerance for these digits' length, amplitude and frequency, and in a single call, these digits could be destined for multiple, different systems: a long-distance provider to enter a calling-card number and access a speed-dial code, a PBX to dial through to another system, followed by access to a bank machine. Without obtaining the feedback received after sending each digit, it's unclear how you could determine what they mean. The cost implication for providers is that for every call being monitored but not recorded, a DTMF-tone receiver must be reserved, significantly increasing the number provisioned in a system.

Other caller-initiated signals, such as pressing keys programmed to initiate special features, also must be reported. This capability is particularly important in GSM systems because they don't initiate features using strings of digits. The technical and interpretation problems are less because these signals' destination usually is the originating system and not an unknown device further down the call path.

Another capability in J-STD-025-A is the reporting of signals sent to a phone. They include types of ringing, strings of letters and digits sent to a display — particularly applicable to wireless phones — and any tones or other signals.

Packet Data's Challenges
One vexing surveillance issue is how to handle packet data. If law enforcement has access to the complete call content — although the term "call" doesn't really apply to packet data — there's no problem, but if it's legally allowed to have access only to "call-identifying information," a major difficulty arises. Providers either can submit the entire packet and trust law-enforcement agencies to look only at what they're legally entitled to, or they can heavily process the packet to separate call content from call-identifying information. There's also the difficulty of defining call-identifying information in the context of packet-data transmissions.

In May, a Joint Experts Meeting concluded that although it's feasible to examine only the outermost protocol layer, this portion often wouldn't contain the required call-identifying information. If call-identifying information can't be extracted from packets, then law enforcement would receive packets that contain data beyond what they're legally entitled to and entire packets that might be irrelevant to the subject being monitored.

As packet-data protocols become more sophisticated, law enforcement agencies may become the victim of "be careful what you wish for because you might get it." They could end up monitoring virtually all packet traffic in order to segregate out small portions of the small fraction of packets that they're legally entitled to monitor.

Misery Loves Company
New telecom technologies are creating increasing challenges for dealing with legal surveillance of communications. Every law-enforcement agency can cite cases where crimes could have been prevented if better monitoring were routinely available, and every civil-liberties organization can point to rogue law-enforcement agents who abused their powers to further personal agendas or entire law-enforcement agencies that unfairly targeted certain people or groups.

Governments are left in the position of trying to find a balance. But by the time the FCC and other U.S. government agencies have finished considering these issues and making decisions, strong encryption technology might mean that smart criminals can't be monitored at all.

Crowe (crowed@cnp-wireless.com) is a wireless-standards consultant and editor of Cellular Networking Perspectives, a wireless-standards and -technology bulletin.