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Introduction to DNSSEC

Anyone who supposes that Internet payments, sending of personal data or sensitive information in the electronic world are absolutely secure today, is wrong. To avoid inconvenience to the website or domain users, they need to be adequately secured.

The most effective way to protect domains is to add an extra level of security, known by the acronym DNSSEC – Domain Name System Security Extensions. Adding it to a domain is easy, just ask your Authorised Registrar (more information below).

What is it?

It is a system that prevents hackers from redirecting a user to the wrong web address and in this way to obtain sensitive data, which can be subsequently misused.

How does it work?

Imagine entering your bank’s address into the address bar of the browser (e.g. www.bank.sk). In this form it is visible just for us – users. The Domain Name System (or DNS for short) provides a „translation“ of this form of address into a computer-readable form (it means IP address e.g. „“) – because the browser searches for the requested page based on the IP address.

In that short time, while the DNS is „translating“ the domain into an IP address, sensitive data may be redirected, stolen or misused. So you may appear on a seemingly identical page, but in reality it is not so. Even the address bar in the browser looks the same like you entered it there.

Thus, the average user does not have a chance to recognize that his device is under attack.


Because only thanks to the DNSSEC system can the web browser check if the address has not been changed somewhere along the way (during the „translation“) by the attackers. By applying DNSSEC, you will secure the website throught the so-called encryption key, thanks to which the user „lands“ where he should appear and will not be redirected to a fake address.

After all you don’t want the users of your website to end up in the hands of scammers!

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For a better understanding of DNSSEC, watch the video (in Slovak language with English subtitles).

How do I know if a domain has DNSSEC?

For detailed verification of DNSSEC it is possible to use e.g. the https://dnsviz.net/ service.

After loading this website simply write the domain to the search box, including the .sk extension, and the system will provide all available data to you. Red color and also an alert icon will alarm you that the domain is not secured by the DNSSEC service.

In some web browsers, there may also be available an extension that allows you to view similar information directly through the browser.

Where can I get it for my domain?

You can ask for DNSSEC through an Authorised Registrar of your domain, because each Registrar has this service available in the SK-NIC system. If you do not know who is the Authorised Registrar of your domain, you can find it on our website on the right in the „Search Domain“ section or by using the WHOIS service.

DNSSEC Statistics for .sk

We introduced DNSSEC in April 2019. On the Virtuálnô.sk portal, in the graphs section, you can see how the number of .sk domains secured by the DNSSEC service has grown.

What is the technology behind DNSSEC?

And now more technically – DNSSEC is the set of technical specifications for the Domain Name System (DNS) which provide the DNS client with verification proving that the data received from the DNS server are authentic.

DNSSEC is using asymmetric encryption – one key for encryption and another one for decryption. Similar principle is being used for encryption and electronic signing of emails (OpenPGP, S/MIME). Holder of the domain that uses DNSSEC generates pair of keys – one private key and one public key (or its registrar provides these keys). Technical details of the domain are subsequently electronically signed by the private key. Public key, stored with the superior authority of the domain, is then used for verification of the authenticity of the technical data through verification of the validity of this signature via the entire hierarchy of the superior signatures all the way to the root one.

After launch of DNSSEC, the technical data of the top level domain .sk will be signed and registry manager SK-NIC, a.s. will hand over the public key to this signature to its own superior authority – to the worldwide manager of the root servers of DNS. This will create hierarchy which will ensure credibility of the data as long as it is not breached at any point, i.e. unless there are errors or misconfigurations, and thus providing that all electronic signatures are all right.

Security Bottlenecks of DNS

Infrastructure of DNS (abbreviation from Domain Name System) provides translation of the domain names into IP addresses and vice versa, but by design it does not have any protection against spoofing of the false data within this communication. For example, if the address “www.sk-nic.sk” is entered into a browser, it can be modified within system communication to a false IP address, while the address line of the browser still displays “www.sk-nic.sk”, hence user will not normally notice, that the browser has displayed a false website in reality. Standard protection via HTTPs won’t necessarily be sufficient in this case, because the HTTPs certificate might not be issued by a trustworthy authority and the DNS communication also runs across a different layer of communication. On the contrary, DNSSEC is trustworthy in such a case, since DNSSEC has its own verification of authenticity, the DNS manager is controlled in various ways and it is not created arbitrarily as is the case with the commercial certification authorities.

In time of creation of the DNS system at the beginning of 80-ties, there was no special attention paid to the security mechanisms of this protocol. Computers of that time were significantly less powerful, asymmetric cryptography (using pair of public and private keys) was still just a new concept and global computer network was significantly smaller with relatively lower number of interconnected people and institutions who mutually knew each other. Over the past 30 years, the use of internet increased dramatically and the DNS protocol became vulnerable, which required creation and use of additional security mechanisms.

There are several major security risks of the DNS system:

  1. DNS hijacking: Computer is opening the website using the IP address provided upon the query to the DNS server. In the case of DNS hijacking, the attacker changes the DNS settings of the computer in such a way, that whenever the computer sends DNS query for IP address translation, instead of the authentic DNS of the internet provider the computer is connected to the false DNS server controlled by the attacker. Such an attack usually occurs if there is a malicious code infection within the computer, e.g. DNS altering trojan. The malicious code changes the DNS settings and replaces address of the authentic DNS server by the address of the malicious server after it infects the computer. As a result, the affected computer would not receive the correct IP address of the requested webpage, but the malicious IP address which is directing the user’s traffic to the website of the attacker and the web browser thus displays a malicious website.
  1. DNS Cache Poisoning: By DNS cache poisoning we call a situation when instead of the authentic record, malicious data are stored in the cache memory of a computer. For example, if we enter website “sk-nic.sk” for the first time, our computer will send the DNS query to the corresponding DNS server and its answer is stored in DNS cache memory together with the time stamp specifying how long this record is valid. If during this time period we again enter “sk-nic.sk”, our computer will not be asking the DNS server, but will retrieve IP address from the DNS cache memory. In the case of cache poisoning, DNS attackers are using malicious tricks in order to force the computer to save false DNS records containing IP addresses of malicious websites controlled by the attackers. It’s obvious what can happen once these are used.
  2. Electronic mail: When email messages are being sent from one server to another, the email servers are sending DNS query along in order to receive IP addresses of the email servers corresponding to the email addresses of the recipients. In this case, the attackers can utilize their malicious methods to force email servers to redirect all or selected electronic mail to the servers of the attacker, whereas attackers can subsequently obviously read all the (sensitive) data contained in the email.

However, this list of security risks is not exhausting, there exists other threats as well.

DNSSEC helps to secure against these as well as other forms of attack.