united-states data-ownership data-storage child-abuse pornography
Legality of data &quot;chunking&quot; concerning child pornography
<p>Recently, I've become interested in distributed, peer-to-peer (p2p) file sharing, including BitTorrent (en.wikipedia.org/wiki/BitTorrent) and the InterPlanetary File System (ipfs.io) (IPFS). This question specifically concerns IPFS.</p>

<p>IPFS is very complicated for non-technical people, so I'll try and break it down for the purpose of this discussion:</p>

<p>In IPFS, you can add data to the global file system, which produces a "hash" (a string uniquely identifying the data) that you can share with others. Data in IPFS is content-addressed, meaning that instead of using URLs or locations for data, it uses fingerprints of the data itself. This has several useful characteristics:</p>

<ul>
<li>anybody on the network with the same data can serve it to you, reducing the burden on a web server and eliminating the waste of bandwidth that is HTTP;</li>
<li>data can remain available even after the original host fails, which makes archiving data much more reliable on IPFS;</li>
<li>and there is no central system that can fail, like DNS resolvers, that can prevent the system from operating (aside from, of course, normal internet infrastructure).</li>
</ul>

<p>When sharing on IPFS, you aren't actually sending whole files to peers; instead, these files are broken apart into "blocks" of data which are retrieved separately (and often from different peers altogether). These blocks are re-assembled at the end to form the complete data.</p>

<p>Now, suppose someone is sharing child pornography via IPFS. Under U.S. law, the mere possession of child pornography is illegal, so the sender is certainly acting illegally. The recipient of these files, after assembling the blocks to form the files, are now in possession of content that visually depicts minors engaging in sexual activity. However, would an intermediary node (hypothetically) that may have cached a block needed to form the violating data be guilty of possession? The block alone cannot represent the visual activity that constitutes illegal material, and in fact, the hash representing the block can represent any such block with the same data (since the hash identifies the data, not a location), so its entirely possible (if slightly improbable) that the same hash for a block used in child pornography could be a block used to represent part of a Disney movie. For example, these two sentences, broken down into uniquely identifiable chunks of two:</p>

<pre><code>I have two cats in my house.
I |ha|ve| t|wo| c|at|s |in| m|y |ho|us|e.
</code></pre>

<p>and</p>

<pre><code>You should burn in Hell.
Yo|u |sh|ou|ld| b|ur|n |in| H|el|l.
</code></pre>

<p>You'll notice that both sentences have a common chunk, "in". Under US law, would someone who possesses this block, "in", be responsible for its use in all contexts, such as in the second sentence?</p>

<p>Obviously, in real data these chunks are between 256 kilobytes and 2 megabytes, so the chance for collision is greatly reduced, but by design of the system, content addressing allows for the avoidance of duplicate data. My question is how that affects legal regulations concerning said data.</p>

<p><a href="https://www.law.cornell.edu/uscode/text/18/2252" rel="nofollow noreferrer">18 U.S. Code § 2252</a> defines a crime and punishment for <em>knowingly</em> transporting, or reproducing for distribution by any means, visual depictions involving the use of a minor engaging in sexually explicit conduct.</p>

<p>Here are some <a href="http://www.mad.uscourts.gov/resources/pattern2003/html/patt05tl.htm" rel="nofollow noreferrer">sample jury instructions</a> that rephrase this and give definitions for each of these terms. Here are <a href="http://www.ca11.uscourts.gov/sites/default/files/courtdocs/clk/FormCriminalPatternJuryInstruction.pdf" rel="nofollow noreferrer">some others</a> (at p. 469). <a href="http://cdn.harvardlawreview.org/wp-content/uploads/pdfs/vol_122_child_pornograph_the_internet.pdf" rel="nofollow noreferrer">This law review article</a> discusses the knowledge requirement of this statute.</p>

<p>It would be an easy argument that the operators of the intermediary nodes do not have the requisite knowledge of the material flowing over their networks and computers to be implicated by section 2252, especially when they are broken down into chunks that can only be re-assembled at the destination.</p>

<p><a href="http://caselaw.findlaw.com/us-9th-circuit/1391767.html" rel="nofollow noreferrer">United States v. Kuchinski, 469 F.3d 853 (9th Cir. 2006)</a> is an example of a case where a defendant was found to <em>not</em> have the requisite knowledge of child pornography that was found in his browser's cache folders. These were complete files, no assembly required. However, the court said:</p>

<blockquote>
  <p>where a defendant lacks knowledge about the cache files, and concomitantly lacks access to and control over those files, it is not proper to charge him with possession and control of the child pornography images located in those files</p>
</blockquote>

<p>An IPFS user has no more knowledge of the pieces being passed through their computer than this defendant did of his cache (unless of course they are the source or destination).</p>
