Bitcoin blockchain is growing big, yet its transaction capacity hit its limits in 2017. One solution heavily discussed within the bitcoin community is to let it grow faster by increasing size of the blocks. However, making transactions smaller instead of blocks bigger is more sustainable and also brings other additional benefits. In this paper, we focus on space wasted by non-cryptographic use of hashes and uncompressed numbers within transaction inputs. In our analyses, we show that transactions can be made approximately 16% smaller, depending on their complexity.
@inproceedings{zima_inputs_reduction_2018,
title = {Inputs {Reduction} for {More} {Space} in {Bitcoin} {Blocks}},
author = {Zima, Michal},
shorttitle = {Inputs Reduction},
isbn = {978-1-5386-7204-4},
url = {https://ieeexplore.ieee.org/document/8525401/},
doi = {10.1109/CVCBT.2018.00020},
language = {en},
booktitle = {2018 Crypto Valley Conference on Blockchain Technology ({CVCBT})},
publisher = {IEEE},
year = {2018},
pages = {112--115}
}We address the problem of a trustless decentralised exchange of cryptocurrencies. Centralised exchanges are neither trustworthy nor secure. As of 2017, there has been more than 25 million US dollars’ worth of cryptocurrencies stolen from (or by) centralised exchanges. With Coincer we allow any two users to exchange their diverse cryptocurrencies directly between them, yet with no need to trust each other. Former approaches either do not do without a server or rely on a trusted issuer of exchangeable tokens. Our approach is to fully eliminate any elements susceptible to becoming a single point of failure. Coincer therefore leverages an efficient anonymous P2P overlay and an atomic protocol for exchanging money across different cryptocurrencies. It is implemented as free software and has been successfully tested with Bitcoin and Litecoin.
@inproceedings{zima_coincer_2017,
title = {Coincer: {Decentralised} {Trustless} {Platform} for {Exchanging} {Decentralised} {Cryptocurrencies}},
author = {Zima, Michal},
shorttitle = {Coincer},
isbn = {978-3-319-64700-5 978-3-319-64701-2},
url = {https://link.springer.com/10.1007/978-3-319-64701-2_53},
doi = {10.1007/978-3-319-64701-2_53},
language = {en},
booktitle = {Network and System Security: 11th International Conference, {NSS} 2017, Helsinki, Finland, August 21--23, 2017, Proceedings},
editor = {Yan, Zheng and Molva, Refik and Mazurczyk, Wojciech and Kantola, Raimo},
volume = {10394},
publisher = {Springer International Publishing},
address = {Cham},
year = {2017},
pages = {672--682}
}Sending money in cryptocurrencies is majorly based on public keys or their hashed forms—“addresses.” These long random-looking strings are user unfriendly for transferring by other means than via copy-and-paste or QR codes. Replacing such strings with identifiers chosen by users themselves would significantly improve usability of cryptocurrencies. Such identifiers could be memorable, easier to write on paper or to dictate over phone. Main challenge lies in designing a practically usable decentralised system for providing these identifiers. Former solutions have been built as centralised systems or come with nonnegligible limitations. Our solution is reminiscent of a prevalent e-mail system, which is an already user friendly and desirably decentralised system. It is shown that our approach is directly applicable also to other systems that use long cryptographic identifiers.
@inproceedings{zima_cryptoaddresses_2016,
title = {Sending {Money} {Like} {Sending} {E}-mails: {Cryptoaddresses}, {The} {Universal} {Decentralised} {Identities}},
author = {Zima, Michal},
volume = {233},
issn = {2075-2180},
shorttitle = {Sending {Money} {Like} {Sending} {E}-mails},
url = {https://arxiv.org/abs/1612.04982},
doi = {10.4204/EPTCS.233.5},
language = {en},
booktitle = {Proceedings 11th Doctoral Workshop on Mathematical and Engineering Methods in Computer Science, {MEMICS} 2016, Tel{\v{c}}, Czech Republic, 21st-23rd October 2016.},
journal = {Electronic Proceedings in Theoretical Computer Science},
month = dec,
year = {2016},
pages = {52--60}
}We address the problem of a secure direct communication of two arbitrary peers in a P2P network without knowing each other’s IP addresses. An efficient solution to this problem will provide a practically usable way of communication to privacy-sensitive P2P applications. Traditionally, P2P architectures view this problem as a problem of mutual anonymity of a message sender and receiver, but usual solutions suffer from various inefficiencies or complexities. By looking at the problem from a perspective of an ad-hoc network, we are able to apply a familiar approach of multihop communication and ad-hoc routing algorithms to a P2P overlay. Introduced usage of a public key as a node’s identifier adds further security features, including data integrity through digital signatures, or end-to-end encryption. Proposed P2P overlay has been successfully used for building a decentralised cryptocurrency exchange Coincer.
@inproceedings{zima_hladka_adhoc_p2p_overlay_2016,
title = {Cryptography {Enhanced} {Ad}-{Hoc} {Approach} to {P2P} {Overlays}},
author = {Zima, Michal and Hladk{\'{a}}, Eva},
isbn = {978-1-5090-2088-1},
url = {https://ieeexplore.ieee.org/document/7568378/},
doi = {10.1109/HPCSim.2016.7568378},
language = {en},
booktitle = {Proceedings of the 2016 {International} {Conference} on {High} {Performance} {Computing} \& {Simulation}},
publisher = {IEEE},
month = jul,
year = {2016},
pages = {517--522}
}Last updated: 2018-07-14