Network Working Group IAB Request for Comments: 2804 IESG Category: Informational May 2000
IETF Policy on Wiretapping
Status of this Memo
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2000). All Rights Reserved.
Abstract
The Internet Engineering Task Force (IETF) has been asked to take a position on the inclusion into IETF standards-track documents of functionality designed to facilitate wiretapping.
This memo explains what the IETF thinks the question means, why its answer is "no", and what that answer means.
The IETF has decided not to consider requirements for wiretapping as part of the process for creating and maintaining IETF standards.
It takes this position for the following basic reasons:
- The IETF, an international standards body, believes itself to be the wrong forum for designing protocol or equipment features that address needs arising from the laws of individual countries, because these laws vary widely across the areas that IETF standards are deployed in. Bodies whose scope of authority correspond to a single regime of jurisdiction are more appropriate for this task.
- The IETF sets standards for communications that pass across networks that may be owned, operated and maintained by people from numerous jurisdictions with numerous requirements for privacy. In light of these potentially divergent requirements, the IETF believes that the operation of the Internet and the needs of its users are best served by making sure the security properties of
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connections across the Internet are as well known as possible. At the present stage of our ignorance this means making them as free from security loopholes as possible.
- The IETF believes that in the case of traffic that is today going across the Internet without being protected by the end systems (by encryption or other means), the use of existing network features, if deployed intelligently, provides extensive opportunities for wiretapping, and should be sufficient under presently seen requirements for many cases. The IETF does not see an engineering solution that allows such wiretapping when the end systems take adequate measures to protect their communications.
- The IETF believes that adding a requirement for wiretapping will make affected protocol designs considerably more complex. Experience has shown that complexity almost inevitably jeopardizes the security of communications even when it is not being tapped by any legal means; there are also obvious risks raised by having to protect the access to the wiretap. This is in conflict with the goal of freedom from security loopholes.
- The IETF restates its strongly held belief, stated at greater length in [RFC 1984], that both commercial development of the Internet and adequate privacy for its users against illegal intrusion requires the wide availability of strong cryptographic technology.
- On the other hand, the IETF believes that mechanisms designed to facilitate or enable wiretapping, or methods of using other facilities for such purposes, should be openly described, so as to ensure the maximum review of the mechanisms and ensure that they adhere as closely as possible to their design constraints. The IETF believes that the publication of such mechanisms, and the publication of known weaknesses in such mechanisms, is a Good Thing.
The issue of the IETF doing work on legal intercept technologies came up as a byproduct of the extensive work that the IETF is now doing in the area if IP-based telephony.
In the telephony world, there has been a tradition of cooperation (often mandated by law) between law enforcement agencies and telephone equipment operators on wiretapping, leading to companies that build telephone equipment adding wiretapping features to their telephony-related equipment, and an emerging consensus in the
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industry of how to build and manage such features. Some traditional telephony standards organizations have supported this by adding intercept features to their telephony-related standards.
Since the future of the telephone seems to be intertwined with the Internet it is inevitable that the primary Internet standards organization would be faced with the issue sooner or later.
In this case, some of the participants of one of the IETF working groups working on a new standard for communication between components of a distributed phone switch brought up the issue. Since adding features of this type would be something the IETF had never done before, the IETF management decided to have a public discussion before deciding if the working group should go ahead. A new mailing list was created (the Raven mailing list, see http://www.ietf.org/mailman/listinfo/raven) for this discussion. Close to 500 people subscribed to the list and about 10% of those sent at least one message to the list. The discussion on this list was a precursor to a discussion held during the IETF plenary in Washington, D.C.
Twenty-nine people spoke during the plenary session. Opinions ranged from libertarian: 'governments have no right to wiretap' - to pragmatic: 'it will be done somewhere, best have it done where the technology was developed'. At the end of the discussion there was a show of hands to indicate opinions: should the IETF add special features, not do this or abstain. Very few people spoke out strongly in support for adding the intercept features, while many spoke out against it, but a sizable portion of the audience refused to state an opinion (raised their hands when asked for "abstain" in the show of hands).
This is the background on the basis of which the Internet Engineering Steering Group (IESG) and the Internet Architecture Board (IAB) was asked to formulate a policy.
The various legal statutes defining wiretapping do not give adequate definitions to distinguish between wiretapping and various other activities at the technical level. For the purposes of this memo, the following definition of wiretapping is used:
Wiretapping is what occurs when information passed across the Internet from one party to one or more other parties is delivered to a third party:
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1. Without the sending party knowing about the third party
2. Without any of the recipient parties knowing about the delivery to the third party
3. When the normal expectation of the sender is that the transmitted information will only be seen by the recipient parties or parties obliged to keep the information in confidence
4. When the third party acts deliberately to target the transmission of the first party, either because he is of interest, or because the second party's reception is of interest.
The term "party", as used here, can refer to one person, a group of persons, or equipment acting on behalf of persons; the term "party" is used for brevity.
Of course, many wiretaps will be bidirectional, monitoring traffic sent by two or more parties to each other.
Thus, for instance, monitoring public newsgroups is not wiretapping (condition 3 violated), random monitoring of a large population is not wiretapping (condition 4 violated), a recipient passing on private email is not wiretapping (condition 2 violated).
An Internet equivalent of call tracing by means of accounting logs (sometimes called "pen registers") that is a feature of the telephone network is also wiretapping by this definition, since the normal expectation of the sender is that the company doing the accounting will keep this information in confidence.
Wiretapping may logically be thought of as 3 distinct steps:
- Capture - getting information off the wire that contains the information wanted.
- Filtering - selecting the information wanted from information gathered by accident.
- Delivery - transmitting the information wanted to the ones who want it.
The term applies to the whole process; for instance, random monitoring followed by filtering to extract information about a smaller group of parties would be wiretapping by this definition.
In all these stages, the possibility of using or abusing mechanisms defined for this purpose for other purposes exists.
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This definition deliberately does not include considerations of:
- Whether the wiretap is legal or not, since that is a legal, not a technical matter.
- Whether the wiretap occurs in real time, or can be performed after the fact by looking at information recorded for other purposes (such as the accounting example given above).
- What the medium targeted by the wiretap is - whether it is email, IP telephony, Web browsing or EDI transfers.
These questions are believed to be irrelevant to the policy outlined in this memo.
Wiretapping is also sometimes called "interception", but that term is also used in a sense that is considerably wider than the monitoring of data crossing networks, and is therefore not used here.
Much of the debate about wiretapping has centered around the question of whether wiretapping is morally evil, no matter who does it, necessary in any civilized society, or an effective tool for catching criminals that has been abused in the past and will be abused again.
The IETF has decided not to take a position in this matter, since:
- There is no clear consensus around a single position in the IETF.
- There is no means of detecting the morality of an act "on the wire". Since the IETF deals with protocol standardization, not protocol deployment, it is not in a position to dictate that its product is only used in moral or legal ways.
However, a few observations can be made:
- Experience shows that tools which are effective for a purpose tend to be used for that purpose.
- Experience shows that tools designed for one purpose that are effective for another tend to be used for that other purpose too, no matter what its designers intended.
- Experience shows that if a vulnerability exists in a security system, it is likely that someone will take advantage of it sooner or later.
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- Experience shows that human factors, not technology per se, is the biggest single source of such vulnerabilities.
What this boils down to is that if effective tools for wiretapping exist, it is likely that they will be used as designed, for purposes legal in their jurisdiction, and also in ways they were not intended for, in ways that are not legal in that jurisdiction. When weighing the development or deployment of such tools, this should be borne in mind.
When designing any communications function, it is a relevant question to ask if such functions efficiently perform the task they are designed for, or whether the work spent in developing them is not, in fact, worth the benefit gained.
Given that there are no specific proposals being developed in the IETF, the IETF cannot weigh proposals for wiretapping directly in this manner.
However, as above, a few general observations can be made:
- Wiretapping by copying the bytes passed between two users of the Internet with known, static points of attachment is not hard. Standard functions designed for diagnostic purposes can accomplish this.
- Correlating users' identities with their points of attachment to the Internet can be significantly harder, but not impossible, if the user uses standard means of identification. However, this means linking into multiple Internet subsystems used for address assignment, name resolution and so on; this is not trivial.
- An adversary has several simple countermeasures available to defeat wiretapping attempts, even without resorting to encryption. This includes Internet cafes and anonymous dialups, anonymous remailers, multi-hop login sessions and use of obscure communications media; these are well known tools in the cracker community.
- Of course, communications where the content is protected by strong encryption can be easily recorded, but the content is still not available to the wiretapper, defeating all information gathering apart from traffic analysis. Since Internet data is already in digital form, encrypting it is very simple for the end-user.
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These things taken together mean that while wiretapping is an efficient tool for use in situations where the target of a wiretap is either ignorant or believes himself innocent of wrongdoing, Internet-based wiretapping is a less useful tool than might be imagined against an alerted and technically competent adversary.
Wiretapping, by definition (see above), releases information that the information sender did not expect to be released.
This means that a system that allows wiretapping has to contain a function that can be exercised without alerting the information sender to the fact that his desires for privacy are not being met.
This, in turn, means that one has to design the system in such a way that it cannot guarantee any level of privacy; at the maximum, it can only guarantee it as long as the function for wiretapping is not exercised.
For instance, encrypted telephone conferences have to be designed in such a way that the participants cannot know to whom any shared keying material is being revealed.
This means:
- The system is less secure than it could be had this function not been present.
- The system is more complex than it could be had this function not been present.
- Being more complex, the risk of unintended security flaws in the system is larger.
Wiretapping, even when it is not being exercised, therefore lowers the security of the system.
Harald Alvestrand Randall Atkinson Rob Austein Brian Carpenter Steve Bellovin Jon Crowcroft Steve Deering Ned Freed Tony Hain Tim Howes Geoff Huston John Klensin
IESG:
Fred Baker Keith Moore Patrik Falstrom Erik Nordmark Thomas Narten Randy Bush Bert Wijnen Rob Coltun Dave Oran Jeff Schiller Marcus Leech Scott Bradner Vern Paxson April Marine
The number of contributors to the discussion are too numerous to list.
[RFC 1984] IAB and IESG, "IAB and IESG Statement on Cryptographic Technology and the Internet", RFC 1984, August 1996.
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9. Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved.
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Acknowledgement
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