Is it legal to send encrypted messages via a post card?
<p>In German law, is it legal to send an encrypted message via a post card?
E.g. encrypt a message text on a computer with RSA and print the Base64 encoding on the post card and send it.
Or is it a requirement that the message content is readable (hand written) plain text?</p>

<p><a href="https://www.gesetze-im-internet.de/englisch_gg/englisch_gg.html#p0058" rel="nofollow noreferrer">Article 10 (1) Basic Law</a> / <a href="https://www.gesetze-im-internet.de/gg/art_10.html" rel="nofollow noreferrer">Art. 10 Abs. 1 Grundgesetz</a>:</p>
<blockquote>
<p>The privacy of correspondence, posts, and telecommunications shall be inviolable.</p>
</blockquote>
<p>You can send whatever you want via postcard (as long as it doesn't constitute a different criminal offense).</p>
<p>Technically, whoever were to decrypt your message, besides the addressee, would probably commit Data Espionage according to <a href="https://www.gesetze-im-internet.de/englisch_stgb/englisch_stgb.html#p1875" rel="nofollow noreferrer">§202a (2) Criminal Code</a> / <a href="https://www.gesetze-im-internet.de/stgb/__202a.html" rel="nofollow noreferrer">§ 202a Abs. 2 Strafgesetzbuch</a>. The second paragraph states that this only applies if the data is transmitted electronically, magnetically, or otherwise in a manner which is not immediately perceptible. I would argue that a non-sealed postcard with an encrypted message would be &quot;not immediately perceptible&quot;.</p>

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