privacy european-union gdpr cryptography cryptocurrency
Do Bitcoin nodes need consent to store EU citizen&#39;s personal data?
<p>The Bitcoin blockchain stores data about bitcoin users. This includes:</p>

<ul>
<li>There bitcoin address, which is linkable to their identity via blockchain analysis</li>
<li>Transactions they have made</li>
</ul>

<p>This would seem to constitute personal data. Would a bitcoin node need consent from any EU citizen who has data on the blockchain? What if an EU citizen made a GDPR request to have their data removed from the blockchain? What about other cryptocurrencies, like Monero, that store transactions but not monero addresses or amounts?</p>

<p>Note that almost any cryptocurrency blockchain can also store arbitrary data (in case the above would not count), although this would be considered a "misuse" of the blockchain in most cases. (There are some blockchains that are designed for arbitrary data storage, however.)</p>

<p>No, consent is not required. There are six lawful bases for processing personal data, see <a href="https://gdpr-info.eu/art-6-gdpr/" rel="nofollow noreferrer">Art. 6</a>. A bitcoin node can base it processing on "performance of a contract" (adding data to the blockchain) or "legitimate interests" (processing existing data).</p>

<p>Bitcoin nodes can be considered joint controllers (<a href="https://gdpr-info.eu/art-26-gdpr/" rel="nofollow noreferrer">Art. 26</a>) because they vote and choose a fork to follow. So the right of erasure (<a href="https://gdpr-info.eu/art-17-gdpr/" rel="nofollow noreferrer">Art. 17</a>) can be exercised against each node. As erasure is not possible in the blockchain, the bitcoin node could have a huge problem. But note that the right of erasure also has conditions, in most cases it is not possible to request erasure. </p>

<p>Of course, the above only applies to the processing of personal data. So it has to be determined first whether personal data is processed. I don't know any details about Monero, so I can't answer that question.</p>
