Distributing files via DNS

Way back when I saw a system for streaming audio via DNS: by using TXT records with a TTL of a few seconds, and updating them in a ring buffer, and by stuffing each record with a fragment of Speex encoded audio, you could get quite viable 2kbps audio streaming. Plus, you ended up with totally automatic and really effective edge-of-network caching.<p>This could have been Dan Kaminsky&#x27;s DNS Radio idea, which he mentions here: <a href="http:&#x2F;&#x2F;dankaminsky.com&#x2F;2004&#x2F;08&#x2F;01&#x2F;50&#x2F;" rel="nofollow">http:&#x2F;&#x2F;dankaminsky.com&#x2F;2004&#x2F;08&#x2F;01&#x2F;50&#x2F;</a><p>However, I haven&#x27;t seen any actual code.

There are some issues that seem difficult to overcome with DNS. DNS is essentially a distributed cache where all records are cached throughout the DNS graph of nodes which the client is using to communicate. One problem that seems to present itself, is how do you update a file with any certainty without reducing the TTL to near zero? Which makes the overall DNS cache performance drop significantly?<p>There are also the problems of the Resource Record lengths, all DNS packets should be less that 512 bytes. I&#x27;m a huge fan of using DNS for exchanging small public data, e.g. public keys, but for large files there are much better options out there.

There&#x27;s nothing to stop anyone from creating new RR types in djbdns and put anything in them they want.<p>I edited dnstxt.c many years ago to print new lines, etc. so I could store, retrieve and cache small, _formatted_ ASCII files from a &quot;zone file&quot; as &quot;TXT records&quot; via DNS. They print nicely on the terminal.<p>And, with dnscurve, you now also have a fast way to encrypt each DNS packet (&quot;small, formatted ASCII file&quot; or whatever you desire) individually in transit.<p>DNS is just a database that happens to be used for a small set of purposes. It&#x27;s fast. And almost everyone connected to the internet uses it.

Cool hack. There are probably more efficient ways of handling entire files, but for small, public&#x2F;cacheable lookups, DNS works great. I used to look up base64&#x27;d usernames to userid&#x27;s via TXT RR&#x27;s. The only downside is potential discoverability (even without axfr), but you could always run it privately.<p>DNS is awesome. Distributed caching, sharding via zones, and UDP protocol with automatic upgrade to TCP for larger records, all at no additional cost.

I remember seeing someone use DNS as a hack for SSH so it could be used without signing into open wifi hotspots (when DNS worked, but HTTP&#x2F;S was intercepted) ...

Neat hack.

I do traffic analysis of DNS traffic to spot things like this. IM&#x2F;IRC, file transfers, rouge-like games, malware C&amp;C...pretty neat stuff all of it, just don&#x27;t think it all goes unnoticed.