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205 lines
8.0 KiB
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<p>There are a great many other applications and projects working on anonymous
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communication and I2P has been inspired by much of their efforts. This is not
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a comprehensive list of anonymity resources - both freehaven's
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<a href="http://freehaven.net/anonbib/topic.html">Anonymity Bibliography</a>
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and GNUnet's <a href="http://www.ovmj.org/GNUnet/links.php3">related projects</a>
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serve that purpose well. That said, a few systems stand out for further
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comparison:</p>
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<ul>
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<li>Morphmix and Tarzan</li>
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<li>TOR / Onion Routing</li>
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<li>Mixminion / Mixmaster</li>
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<li>Freenet</li>
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<li>JAP</li>
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</ul>
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<h2>Morphmix and Tarzan</h2>
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<i><a href="http://www.tik.ee.ethz.ch/~morphmix/">[Morphmix]</a>
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<a href="http://www.pdos.lcs.mit.edu/tarzan/">[Tarzan]</a></i>
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<p>Morphmix and Tarzan are both fully distributed, peer to peer networks of
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anonymizing proxies, allowing people to tunnel out through the low latency
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mix network. Morphmix includes some very interesting collusion detection
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algorithms and Sybil defenses, while Tarzan makes use of the scarcity of IP
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addresses to accomplishs the same. The two primary differences between
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these systems and I2P are related to I2P's <a href="how_threatmodel">threat model</a>
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and their out-proxy design (as opposed to providing both sender and receiver
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anonymity). There is source code available to both systems, but we are not aware
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of their use outside of academic environments.</p>
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<p>Stealing quite directly from the Tarzan paper, the following includes a quick
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comparison of Tarzan, Crowds, Onion Routing (OR), and I2P:</p>
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<table>
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<tr>
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<td style="width: 19%;"></td>
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<td style="width: 27%;" colspan="4">Bad first relay/router</td>
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<td style="width: 27%;" colspan="4">Bad intermediate relay/router</td>
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<td style="width: 27%;" colspan="4">Bad last relay/router</td>
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</tr>
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<tr>
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<td>Information exposed</td>
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<td><b>OR</b></td>
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<td><b>Crowds</b></td>
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<td><b>Tarzan</b></td>
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<td><b>I2P</b></td>
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<td><b>OR</b></td>
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<td><b>Crowds</b></td>
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<td><b>Tarzan</b></td>
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<td><b>I2P</b></td>
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<td><b>OR</b></td>
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<td><b>Crowds</b></td>
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<td><b>Tarzan</b></td>
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<td><b>I2P</b></td>
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</tr>
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<tr>
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<td>Sender activity</td>
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<td>Yes</td>
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<td>Maybe</td>
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<td>Maybe</td>
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<td><b>No</b></td>
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<td>No</td>
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<td>No</td>
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<td>Maybe</td>
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<td><b>No</b></td>
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<td>No</td>
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<td>No</td>
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<td>No</td>
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<td><b>No</b></td>
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</tr>
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<tr>
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<td>Recipient activity</td>
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<td>No</td>
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<td>Yes</td>
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<td>No</td>
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<td><b>No</b></td>
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<td>No</td>
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<td>Yes</td>
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<td>No</td>
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<td><b>No</b></td>
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<td>Yes</td>
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<td>Yes</td>
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<td>Yes</td>
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<td><b>No</b></td>
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</tr>
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<tr>
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<td>Sender content</td>
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<td>No</td>
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<td>Maybe</td>
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<td>No</td>
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<td><b>No</b></td>
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<td>No</td>
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<td>No</td>
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<td>No</td>
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<td><b>No</b></td>
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<td>No</td>
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<td>No</td>
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<td>No</td>
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<td><b>No</b></td>
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</tr>
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<tr>
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<td>Recipient content</td>
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<td>No</td>
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<td>Yes</td>
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<td>No</td>
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<td><b>No</b></td>
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<td>No</td>
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<td>Yes</td>
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<td>No</td>
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<td><b>No</b></td>
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<td>Yes</td>
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<td>Yes</td>
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<td>Yes</td>
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<td><b>No</b></td>
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</tr>
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</table>
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<p>(Original image at <a href="http://dev.i2p.net/~jrandom/wiki/comparison.png">
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http://dev.i2p.net/~jrandom/wiki/comparison.png</a>)</p>
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<h2>TOR / Onion Routing</h2>
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<i><a href="http://freehaven.net/tor/">[TOR]</a>
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<a href="http://www.onion-router.net">[Onion Routing]</a></i>
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<p>TOR and Onion Routing are both anonymizing proxy networks, allowing people
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to tunnel out through their low latency mix network. The two primary
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differences between TOR / OnionRouting and I2P are again related to differences
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in the threat model and the out-proxy design (though TOR is working to provide
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redevous points within the mix network, which will provide recipient anonymity).
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In addition, these networks take the directory based approach - providing a
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centralized point to manage the overall 'view' of the network, as well as gather
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and report statistics, as opposed to I2P's distributed <a href="how_networkdatabase">network
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database</a> and <a href="how_peerselection">peer selection</a>.</p>
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<p>On the technical side, there are 5 main differences between TOR and I2P:</p>
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<ul>
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<li>TOR is centrally managed (trusted directories, only some people fully participate
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in the network with cover traffic) while I2P is fully distributed. This has serious
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anonymity implications for people using TOR that are not one of the TOR nodes,
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since a powerful attacker could determine your identity, or coerce the maintainer
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of TOR's directory server to include untrustworthy nodes.</li>
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<li>TOR is circuit based (with reliable, ordered, bidirectional tunnels), while I2P
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is packet based (with unreliable, unordered, unidirectional tunnels). As with the
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TCP/IP separation, I2P optionally adds TCL-like functionality on top of the packet
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based network by means of mihi's ministreaming library.</li>
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<li>TOR is low latency, while I2P is variable latency (both ASAP and stop+go). This will
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allow I2P to provide a higher level of anonymity by blending the anonymity set of
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different user bases together - for example, filesharing users and militants look
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the same, though make use of different techniques to balance their own anonymity
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and security needs)</li>
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<li>TOR is IP addressed, relying on the security of the IP layer for authenticating
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and securing the message delivery, while I2P is cryptographically addressed.</li>
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<li>TOR is written in C while I2P is written in Java</li>
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</ul>
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<h2>Mixminion / Mixmaster</h2>
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<i><a href="http://mixminion.net/">[Mixminion]</a>
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<a href="http://mixmaster.sourceforge.net/">[Mixmaster]</a></i>
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<p>Mixminion and Mixmaster are networks to support anonymous email against a very
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powerful adversary. I2P aims to provide an adequate means to meet their threat
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model as we reach I2P 3.0 along side the needs of low latency users, providing
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a significantly larger anonymity set. As with TOR and Onion Routing above,
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both Mixminion and Mixmaster take the directory based approach as well.</p>
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<h2>Freenet</h2>
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<i><a href="http://freenetproject.org/">[Freenet]</a></i>
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<p>Freenet is a fully distributed, peer to peer anonymous publishing network.
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As such, generic anonymous communication over it requires the use of the global
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blackboard model - storing data somewhere that the recipient will then check
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for a message. Freenet also does not support the concept of user defined delays -
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it stores and fetches data as quickly as it can, rather than queueing up, pooling,
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delaying, and mixing the data, leaving a hole with regards to long term intersection
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attacks. In addition, there seem to be some performance issues that can arguably
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be attributed to the global blackboard model which will likely rule out interactive
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low latency communication.</p>
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<h2>JAP</h2>
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<i><a href="http://anon.inf.tu-dresden.de/index_en.html">[JAP]</a></i>
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<p>JAP (Java Anonymous Proxy) is a network of mix cascades for anonymizing web requests,
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and as such it has a few centralized nodes (participants in the cascade) that blend
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and mix requests from clients through the sequence of nodes (the cascade) before
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proxying out onto the web. The scope, threat model, and security is substantially
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different from I2P, but for those who don't require significant anonymity but still
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are not satisfied with an Anonymizer-like service, JAP is worth reviewing. One
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caution to note is that anyone under the jurisdiction of the German courts may want
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to take care, as the German Federal Bureau of Criminal Investigation (FBCI) has has
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successfully mounted an
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<a href="http://www.datenschutzzentrum.de/material/themen/presse/anonip3_e.htm">attack</a>
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on the network. Even though the method of this attack was later found to be illegal
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in the German courts, the fact that the data was successfully collected is the
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concern. Courts change their minds based upon circumstance, and this is evidence that
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if a government body or intelligence agency wanted to, they could gather the data, even
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if it may be found inadmissible in some courts later)</p>
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