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Big ZSK Experiment

The Big ZSK experiment is designed to test operating the Yeti root with a 2048-bit ZSK.

RSA 1024 is no longer recommended for cryptography. At some point the ZSK needs to be made longer. Common practice is to adopt 2048 bits keys.

VeriSign gave a presentation at the DNS-OARC 24th workshop, announcing that they will be increasing the root zone ZSK from 1024 bits to 2048 bits in 2016:

Yeti should change to RSA 2048 for ZSK and observe the results. While signed replies will be larger, it is unlikely that we will see increased truncation or fragmentation, as most replies will still be less than 1280 bytes.

Given that this is merely an extension of existing key length, and that the KSK is already signed with the same algorithm and key length, we propose not to require and lab test for this experiment.

This experiment does not require any specific changes on the part of the Yeti root operators or the Yeti resolver operators.

Scope of Test

This experiment will test the behavior of the Yeti root servers and resolvers when we have a 2048-bit ZSK.

Experiment Plan

Each of the three Yeti Distributors will change their ZSK from 1024 bits to 2048 bits. They will use the normal ZSK roll to do this. The entire roll will take 12 days.

Rollback Procedures

If a need to rollback is identified, we will roll to a new 1024 bit ZSK for all Yeti Distributors.

If there is a rollback we will announce it to the Yeti Discuss list as well as on the Yeti website.

What to Measure

We are currently capturing questions at many root servers. We should also change our capture scripts so that they also capture responses.

Since these measurements are occuring at all times, we do not need to add any more caputures. We should look monitor the traffic before and after we lengthen the ZSK to see if there are any changes, such as a drop off of packets or a increase in retries.

We set up checks for the MZSK experiment to confirm that we can lookup and validate a range of zones, using both BIND 9 and Unbound. We will keep these in place for the BGZSK experiment.

The size of answers will increase, but we do NOT expect the average response to fragment. Even a relatively large delegation will be less than 1000 bytes (an example may be .INFO queries). Even so, we will monitor possible impact by using RIPE Atlas measurements to measure some key delegation queries.


This experiment is relatively simple, and requires little preparation.

We can do preparation and start rolling in the new key on 2016-05-09 (Monday). This aligns well with the current ZSK timings for BII, where the ZSK is scheduled to become inactive on 2016-05-11.

TISF would start rolling on 2016-05-13, and WIDE on 2016-05-17.

Report Format

Once the BGZSK experiment is complete, we will produce a final report.

This will include the motivation and actions taken, as well as any observations made during the experiment. The results of traffic analysis will be included, along with a conclusion.

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