Pantos Q&A: Update on TAST and DeXTT prototype research

Apr 11 · 4 min read

After we successfully published the fourth TAST Technical White Paper and released the TAST research prototype we sat down with the Pantos team to talk about the progress so far and the plans for future research and development.

As you may have already seen in the fourth TAST Technical White Paper, two new researchers recently joined the team. Philipp Frauenthaler and Marten Sigwart are both part of the Distributed Systems Group at TU Wien and will work closely together with the existing Pantos team to further develop concepts and approaches for bringing blockchain interoperability closer to viability.

What made you join Pantos? What got you interested in it?

The blockchain space has seen a lot of hype, especially in the last couple of years, promising the “decentralization” of virtually everything. However, the technology is still very much immature. Major technological challenges still need to be solved. One of them is blockchain interoperability. That’s why we joined Pantos, it’s just super exciting to work on a project that’s actually trying to solve one of the core problems in the space.

What are the key findings of the recently released fourth TAST Technical White Paper?

In the recent TAST Technical White Paper, we take a step back from the work we have done so far, and consider the bigger picture of our work: We aim to enhance blockchain interoperability, which poses several challenges. At the beginning of the research project, we discussed a few open questions, which we revisit now with today’s knowledge. Fortunately, in the past nine months, we have gained a lot of insight and expertise and many of the questions from the first white paper are now answered to a large degree.

Finally, we provide a broad outlook on the planned future research, and what our next steps will look like.

Can you explain the concept of ‘deterministic witnesses’ in a simple way?

Whenever a cross-blockchain token transfer happens on DeXTT, the updated token balances need to be synchronized across all blockchains participating in the blockchain ecosystem. This synchronization happens through incentivized witnesses, that is, a witness can win a reward if they propagate the transfer to all other blockchains. However, note that (a) only one witness can win the reward and that (b) a reward leads to another update of token balances. Thus, if the witness which receives the reward was chosen randomly for each blockchain, the balance change caused by the witness reward would be different across all blockchains. Another synchronization of balances would be required, which again causes another round of incentivized witnesses to propagate the information, which again leads to a random reward, and so on. Hence, choosing the witness at random is not viable.

Instead, we thought about a way to select the same witness for the reward across all blockchains. This allows us to update the balances on all blockchains, in the same way, avoiding the need for synchronization. This is where deterministic witnesses come into play. Deterministic means the witnesses are chosen in a pre-determined way on all blockchains, that is, the same witness is selected. The difficulty here is to still make the selection process random in the sense that all witnesses have the same chance of being selected as the winner.

The TAST research prototype ( ‘DeXTT: Deterministic Cross-Blockchain Token Transfers’) is available on GitHub now. Can you tell us a little more about this prototype?

The prototype available on GitHub demonstrates how the concepts and approaches we have developed and described in theory can be implemented in practice.

First, the provided documentation gives a technical description of the DeXTT protocol. We describe how the DeXTT protocol can be used to transfer tokens without binding them to a single blockchain. Second, we provide an implementation of DeXTT using Solidity. We have used this implementation to evaluate the functionality and performance of DeXTT — the results have been submitted to an academic conference and, provided the paper is accepted for publication, will be available soon.

Granted, this prototype is not usable as a product yet, there is no easy-to-use wallet application and we still need to find solutions to certain technological challenges. Nevertheless, it brings the research project one step closer to its ultimate goal, which is fostering interoperability between blockchains.

What are the planned next steps in the TAST research project?

Currently, we are exploring approaches that build on the technologies of DeXTT but eliminate some of its limitations. In particular, we aim to mitigate the synchronization costs imposed by DeXTT due to the need to propagate any balance change across all blockchains of the blockchain ecosystem. Ideally, a cross-blockchain token transfer causes a state change only on the two blockchains directly involved in the transfer. We will present these approaches in detail in upcoming White Papers and academic publications.

About Pantos

As the first multi-blockchain token system, Pantos aims to bring blockchain projects closer together, improve communication between developers, researchers and users, and set innovative standards for cross-chain token transfers.

The goal is to serve as a lighthouse project in an increasingly fragmented blockchain space. With multiple blockchains serving all kinds of different purposes, Pantos is seeking to allow these projects to talk to one another in a standardised way. This will speed up innovation by creating a link between blockchains which then can scale together.

To get the latest news on the progress of the Pantos project you can follow our official channels:


The first multi-blockchain token system. Made with ♥ and care in Vienna by @bitpanda.


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The first multi-blockchain token system. Made with ♥ and care in Vienna by @bitpanda.



The first multi-blockchain token system. Made with ♥ and care in Vienna by @bitpanda.

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