32

Anonymity means that nobody knows your real identity (on the Internet).

Untraceability means that nobody is able to trace back your actions to you.

It appears to me that Anonymity and Untraceability is the same thing: if nobody knows my real identity on the Internet, how are other users going to trace my action to me? Similarly, if no one can trace my actions to me, I am considered to be anonymous.

I am unsure if my line of argument is correct and how to define the relationship between Anonymity and Untraceability.

What is the relationship between Anonymity and Untraceability, and how are they different?

30

The two notions are actually different. Anonymous systems usually are untraceable as a side effect but the reverse isn't true.

Consider, for instance, voting. The process is usually not anonymous: you have to prove you identity and rights to vote before you can do so and the system will keep track of how many votes you have cast. But it can also be untraceable (as an additional property) in the sense that nobody could find out what you actually voted for.

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    In that last sentence did you mean untraceable rather than anonymous? – stonemetal Dec 1 '14 at 18:53
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    I have always wondered about this, especially if you mail your vote in. How does non-anonymous untraceable voting work, when your mail-in ballot has your name practically attached to the ballot? Do we have to just trust that the two get separated before your votes are actually looked at? – Michael Dec 2 '14 at 3:23
  • @Michael I'm not aware of any mail-in voting system that's demonstrably untraceable and used in political elections (maybe in some geek clubs). That's why some locales don't do mail-in votes. – Gilles Dec 2 '14 at 12:48
  • @Michael: yes. In Washington state the registration and routing information and the voter's signature/affidavit all go on the outer envelope, while the ballot itself is normally separated from the outer envelope sealed in an inner privacy envelope. So it's fairly simple to ensure the two are separated before the ballot is counted. – Mike McManus Dec 2 '14 at 22:57
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    "[Voting] ... is usually not anonymous: you have to prove [your] identity and rights [etc and these will be tracked, but] it can also be untraceable (as an additional property) in the sense that nobody could find out what you actually voted for." I think this conflates at least two separate things under the single word "voting". Registering to vote isn't anonymous or untraceable. Likewise requesting a ballot paper (which in some locales is required in addition to registering). But the ballot paper itself is anonymous, & hence untraceable to you (short of dusting for fingerprints, etc). – sampablokuper May 23 '16 at 11:28
17

The distinction is subtle, but in some ways, quite important.

If an action is untraceable, it's impossible to determine where it came from or who did it. This implies a level of anonymity, in that you can't name the person who carried out an action. However, it may be possible to trace an action back to a certain identity without being able to name that identity. Consider a criminal investigation - a serial killer may have a particular MO, or an infamous thief may have a calling card that they leave at the scene. There may be evidence that allows the police to work out how the perpetrator got in, how they committed the crime, and how they got away. In this case, the action is certainly traceable - but the police still don't know who committed the crime, so in that sense, the action is anonymous. In the online world, this is fairly commonplace, with online identities forming a calling card for your actions. If you use some suitably secure method of authentication, you can communicate with someone in a manner that is traceable in that they can be certain that it's you who sent the message, but it's anonymous because they don't know who you actually are.

On the flip side, your online identity may be well-known, and you could use a disposable mail system, or ToR, or hack into a computer and leave a signed message, so that the recipient knows that it came from you, but they can't prove when or where you sent it from - so that message isn't anonymous, because they know it's from you, but it's untraceable because they can't tell when or where the message came from. If you hadn't told them that the message was from you, it would also have been anonymous - but if you chose to claim that the message wasn't from you, nobody would be able to refute that claim.

5

It depends on what you mean by "untraceable". By definition, you can't be anonymous if adversaries can trace your actions back to your identity. However, you can remain anonymous to adversaries who can trace your actions back to your location, as long as you've moved on by the time they do that, and as long as there aren't compromising records.

Conversely, you can be untraceable without being anonymous. Consider my identity "mirimir". It's far from anonymous, with a Gravatar and GnuPG key, and much online activity. But tracing it back to my identity would be hard.

Another useful concept here is "nonattributable": "not capable of being attributed to a particular source or cause". Anonymous and nonattributable are close, I think.

5

I would argue for the following definitions:

Pseudonym is a fictitous name used to protect your real identity.

Untraceability means that nobody is able to trace back your actions to gain any info even related to your pseudonym or real identity.

Anonymity means that there is no way to identify you uniquely from any other individual (although another alternate meaning is "something which has no name").

In one sense a pseudonym therefore provides anonymity as no one can uniquely identify your real identity. But in another sense having a known pseudonym is the opposite of anonymity as you have a name that uniquely identifies you within the group of all other pseudonyms.

Consider for example a Bitcoin transaction. A Bitcoin transaction occurs between two accounts that are each essentially identified by highly unique number:

  • The two accounts numbers are pseudonyms that protect the real identities of those involved and therefore provides anonymity for the owner's real identities.
  • On the other hand, all actions related to an account are purposefully highly traceable as all transactions are recorded in a public ledger.

This is essentially the opposite of the voting example given by Stephane where there is untraceability but not anonymity. The untraceability is only in terms of which vote you cast though, and not that you cast it or where you cast it as that info is needed to prevent individuals voting more than once.

  • Isn't Bitcoin pseudonymous rather than anonymous? That is, all transactions involving a specific identity share that identity (a pseudonym), but there might be no easy way to connect that identity to a real-life identity (a person). – a CVn Dec 2 '14 at 13:21
  • @MichaelKjörling Thanks! I've added some info to account for the subtle difference between anonymity and having a pseudonym (which I wasn't even fully aware of). I would say that most pseudonyms can also provide further anonymity as multiple people can use the same pseudonym, such as a bitcoin account belonging to a company instead of an individual. – Silveri Dec 2 '14 at 14:48

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