DoH vs DoT vs DNSSEC: Privacy and DNS Security Explained

People often group DoH, DoT, and DNSSEC together, but they target different risks and reinforce one another when layered correctly.

Classic DNS travels in clear text, so on-path observers can read or tamper with queries. DoH and DoT fix that by encrypting the hop between your device and a recursive resolver. DNSSEC is different: it signs the DNS data itself so a resolver can prove authenticity and integrity.

Once you separate transport privacy from data integrity, choices get easier. Use DoH or DoT for confidentiality on the wire, and use DNSSEC so answers can be verified as genuine. In many networks, you’ll want both.

What Each Technology Does

Your device’s stub resolver asks a recursive resolver for records (A, AAAA, MX, TXT). The recursive resolver walks the hierarchy (root, TLD, zone) to find authoritative data and returns it. DoH and DoT protect the stub-to-recursive hop. DNSSEC protects the authenticity of the records that authoritative servers publish and your resolver returns.

DNS Over HTTPS (DoH)

DoH carries DNS messages inside standard HTTPS, typically on port 443 using HTTP/2 or HTTP/3. Because it blends with web traffic, DoH often works on locked-down networks that only permit browsing. TLS authenticates the resolver via its certificate and encrypts queries and responses in transit. DoH does not hide which resolver you contact, and it does not validate the origin of DNS data; that validation is DNSSEC’s job.

DNS Over TLS (DoT)

DoT wraps DNS directly in TLS on port 853, avoiding HTTP entirely. It offers the same hop-level confidentiality and server authentication as DoH but presents as a distinct, easily identified service. That separation simplifies firewalling and QoS, though some networks block 853 while allowing 443. With persistent connections and TLS session resumption, DoT amortizes handshake cost and keeps latency low.

DNS Security Extensions (DNSSEC)

DNSSEC adds cryptographic signatures (RRSIG) to DNS data and publishes public keys (DNSKEY) with a chain of trust from the root downward. Delegations carry DS records that link a child zone’s keys to its parent. A validating resolver checks signatures and refuses to return data that fails validation. DNSSEC also supports authenticated denial of existence via NSEC or NSEC3, proving a name truly does not exist. DNSSEC does not encrypt traffic; queries and answers remain visible unless you also use DoH or DoT.

Privacy Properties

“Privacy,” here, means shielding your DNS questions and the resolver’s answers from on-path observers. Both DoH and DoT deliver that confidentiality, so Wi-Fi peers, local gateways, or transit providers can’t read or silently alter your DNS traffic. The resolver still sees your source address and requested names, and destination sites remain observable at the IP layer. DoH’s use of port 443 gives it a higher chance of passing through restricted networks; DoT’s dedicated port makes it cleaner to identify and manage as DNS.

Integrity and Authentication

Integrity belongs to DNSSEC. A validating recursive resolver checks that data is signed and unmodified before returning it. If anything in a signed zone is broken—expired signatures, mismatched keys, or a wrong DS at the parent—the resolver treats the result as bogus and fails the lookup instead of returning tampered data. You can run DoH or DoT without DNSSEC (private channel but unverified content), or DNSSEC without DoH/DoT (authentic data but visible on the wire). Combining them yields authenticated data and an encrypted path.

Performance and Operational Trade-offs

Latency depends more on resolver proximity, cache hit rates, and connection reuse than on protocol branding. DoH multiplexes many outstanding queries on a single HTTPS connection, and modern stacks keep HTTP/2 or HTTP/3 sessions warm. DoT supports multiple in-flight queries on one TLS session and benefits from session resumption. Operationally, DoT’s dedicated port helps with traffic classification and capacity planning; DoH’s camouflage in 443 reduces the chance of being blocked but makes differentiated QoS and observability trickier. For troubleshooting, you’ll lean on client tools and resolver logs since packet captures won’t reveal encrypted payloads.

When to Combine and How to Deploy

The durable pattern is simple: point clients at a recursive resolver that validates with DNSSEC, and connect to that resolver over DoH or DoT. If you run your own resolver, enable validation, ensure reliable time sync, and monitor signature failure rates. If you rely on a public resolver, prefer one that clearly documents validation behavior and uptime SLOs.

Home and Small Office

Enable encrypted DNS on endpoints or your gateway, choosing a trustworthy resolver that supports both DoH and DoT. Major operating systems and browsers can auto-upgrade to encrypted DNS for known providers. If you use filtering, make sure it doesn’t contradict DNSSEC: avoid fabricating unsigned answers for names in signed zones, or perform filtering upstream before validation so clients see coherent, validated data.

Enterprise

Centralize resolution through organization-managed recursive resolvers that validate and, if needed, forward upstream over DoT or DoH. Enforce device policy to prevent bypassing corporate resolvers. For split-horizon internal zones, sign what you can; where you can’t, scope validation exceptions narrowly and document negative trust anchors with expiration. Track validation failure spikes—they often indicate upstream key rollover issues or delegation mistakes rather than transport problems.

Public and Guest Networks

Offer both DoT and DoH when feasible. If you must intercept legacy port-53 traffic, state that policy openly and provide opt-in encrypted endpoints. Trying to block DoH by enumerating provider IPs is brittle and risks collateral damage to unrelated HTTPS traffic.

Common Pitfalls and Myths

“DoH is more private than DoT” is a myth; both rely on modern TLS for confidentiality and authentication. Port-443 camouflage helps with reachability, not cryptography. “DNSSEC is slow” is overstated; with caching and modern crypto, overhead is modest compared with the protection against cache poisoning. A frequent foot-gun is local ad-blocking that injects bogus answers for names inside signed zones while validation is enabled; the result looks like an outage. Align filtering with validation or move filtering upstream of the validator.

Quick Decision Guide

If you need a fast rule: use a validating resolver; enable DoH or DoT on every client; prefer providers and internal resolvers that publish validation status; sign any zones you operate; and treat validation failures with the same seriousness you give TLS certificate errors.

Feature Comparison at a Glance

DoH: encrypts and authenticates the stub-to-resolver hop via HTTPS on port 443; supports HTTP/2 and HTTP/3 multiplexing; blends with web traffic. DoT: encrypts and authenticates the stub-to-resolver hop via TLS on port 853; DNS-specific framing; easy to classify and manage. DNSSEC: authenticates data origin and integrity from authoritative sources to the resolver, with NSEC/NSEC3 for authenticated denial of existence; adds no confidentiality without DoH or DoT. The strongest posture: DoH or DoT plus DNSSEC validation.