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Theme fund: NGI0 PET
Start: 2019-04
End: 2019-04
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Software engineering


Implementation of Dining Cryptographers Network

The aim of the proposed project is to design and implement an open source library that implements the so-called Dining Cryptographer's network or DCnet (first proposed by David Chaum in 1998). Existing implementations suffer from poor efficiency (e.g. high computation and/or communication cost) or limited security (e.g. when a malicious participant can disrupt the communication). The project will produce cryptographic primitives and protocols that help to bring untraceable communication (e.g. untraceable instant messaging, file transfer, IP telephony) closer to practice. We will implement the most recent advances in cryptographic research (e.g. zero-knowledge proofs) and engineering (e.g. highly optimized arithmetic on elliptic curves and finite fields) into account to maximize both security and efficiency.

Why does this actually matter to end users?

According to the Universal Declaration of Human Rights established just after the second world war, all humans have a number of inalienable rights. These are quite fundamental rights such as the freedom of association, freedom of movement and freedom of speech. These rights were instituted to protect normal people from those who can wield power over them, such as governments. The rights enable people to collectively counter injustice, corruption (in particular within institutions that are supposed to be incorruptible such as the police, the court and government) and inequality. Surely, it is not a goal in itself of most governments to curb individual rights, at least not in Europe. But when these rights are not respected, things can get out of hand quickly. Human rights are part of social hygiene.

In the datacene era, however, these rights seem to be under threat. People are constantly observed from all angles of the internet. A lot of data and metadata is being collected about their behaviour. Who is talking to whom, when and where. That data can unexpectedly pop up years later, in a completely different context - and be weaponised against them at that time. This pervasive social logging has a chilling effect on the mind of the individual: if everything you do can be used against you at any point in time, it is best to not do anything. So the piling up of data and observational metadata from corporate and private surveillance hurts the collective ability for groups of like-minded people to express themselves and pursue their common interests.

In order to really enjoy these fundamental human rights in the computer age, we need to take countermeasures. We need to restore confidentiality within social groups as a technical principle. Of course, the possibility of regaining confidentiality is also useful for businesses and governments that sometimes need to hold their card close to their chest to prevent espionage. The project will build a communication tool based on sound scientific principles. The tool will continually shuffle 'black boxes' of unknown digital content among a group of people. In some cases, there might be a message inside the box, in other cases the box will be empty. The boxes are all the same size and weight, so you cannot tell which is which from the outside. The content is protected by using complex mathematical operations and protocols that prevent snooping. For a human, this would be very tiring and unpractical. But for a computer, this is just another job it can do in the background. This setup creates so called 'plausible deniability': you cannot know what is being discussed. You cannot know if someone actively participated in a discussion, or just passively participated. And if you use some other level of indirection that hides the remaining data traces like your IP address, no-one (outside the group) can learn anything. Such a scheme significantly reduces the amount of available metadata to outside observers. If we are serious about fundamental rights such as the freedom of association, freedom of movement and freedom of speech in the digital world, tools like this can make a world of difference.

Run by University of Luxembourg

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This project was funded through the NGI0 PET Fund, a fund established by NLnet with financial support from the European Commission's Next Generation Internet programme, under the aegis of DG Communications Networks, Content and Technology under grant agreement No 825310.