Tomas Krizek's blog

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DNS Privacy with DNS-over-TLS (DoT)

Last updated: 2019-11-23

Almost every internet communication begins with a DNS query. These are commonly transmitted over UDP in plain text. DNS over TLS (DoT, RFC 7858) uses a secure channel to communicate with the DNS server. This has two major benefits. First, it hides your queries from 3rd parties (local network operator, ISP, …) during transit. Second, it ensures you receive the query as it was sent from the DNS server and no one has manipulated it in transit (popular with ISPs and port 53/udp).

If you want to take advantage of DoT, one of the options you have is to use a local resolver and forward your queries over TLS to another resolver. However, this comes with another issue - who are you forwarding your queries to? What will they do with your queries? Does their bussiness model include data mining your private data? Be sure to check out the privacy policies of those big DoT providers. (UPDATE 2019-11-23: read this post for even better solution).

In the spirit of decentralization, I’d like to encourage you to consider using a privacy-oriented resolver that doesn’t log your queries or IP address. You may want to consider the resolvers listed at or run by nonprofit organizations, such as CZ.NIC’s ODVR.

It’s important to note DoT only protects your DNS queries. There are other methods to monitor your traffic. One example would be SNI, which sends a domain name in plaintext during TLS handshake. To mitigate these, I’d recommend to use Tor and/or VPN.


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