OpenDHT is a lightweight C++11 Distributed Hash Table implementation software library. It is originally based on Juliusz Chroboczek’s DHT library with many important innovations. OpenDHT is developed by Savoir-faire Linux and licenced under the GNU General Public License version 3.
At the leading edge of innovation, the Ring project — a secure and distributed voice, video and chat communication platform — paves the way for complex theoretical challenges. Through a research agreement, Savoir-faire Linux and Université du Québec à Montréal (UQAM) collaborate to improve the data persistence and indexation in its underlying distributed hash table software library, OpenDHT.
With the financial support of the Natural Sciences and Engineering Research Council of Canada (NSERC), a group of IT students at UQAM are modeling the problems raised by the high technicality of Ring, and implementing robust codes to resolve them. As the research can lead to innovative solutions, Professor Alexandre Blondin Massé who is in charge of the project, is planning to publish the results within the next year.
Already conclusive results: enabling data persistence and reliable data stored for a limited time on the DHT network
Simon Désaulniers is now completing a Bachelor of Computer Science. He has just modeled and implemented a solution to store data for a limited time on the DHT network. With this progress, the users of Ring will soon access messages that are sent to them while they are not connected. This new process makes sure that each message is encrypted when it is stored and intact when it is received.
A major challenge: Solving the DHT Indexation by data research from any related element
Graduate and PhD students seek to resolve the question of DHT Indexation. To contact a Ring user, it is necessary to know his 40-character ID. The DHT indexation will allow users to look for another user’s Ring ID through information he has made public such as his name or a public alias, while preserving his anonymity. Wondering how it’s possible? Marco Rebado, Sylvain Labranche and Simon Désaulniers are precisely devising a solution. In the meantime, feel free to communicate confidentially with Ring!
I am very excited about an initiative that we are spearheading at Savoir-faire Linux which takes aim at the secure communication market. The major issue at large is that you cannot have privacy when there is a centralized server or service which can monitor and measure your communication with others – Big Brother is always watching. The solutions on the market today require that you connect via their service so that they can define a revenue model such as selling advertising or charging usage fees.
Being true to our roots of supporting and developing free software, SFL is developing a communication platform that requires no centralized server to communicate and this leave the power of privacy in the hands of the user.
By adopting the same technology that is used by popular Torrent networks – Distributed Hash Tables (DHT) – the platform creates its own secure network over the Internet by which it can distribute directory functions, authentication and encryption across all systems connected to it – we call it Ring.
So maybe you are asking yourself now:
Okay, it sounds cool but what does that mean for me?
Let’s take a look at some of the advantages:
There is no centralised server so no one can track you and the service can never go down
You control whom you give your ID key to – without knowing your key there is no way to reach you
Its free – as in no charge and also as in GPL
It doesn’t require any configuration setup and no password
It is all encrypted – communication is point to point encrypted for chat, video conference and voice calling up to AES128
It is available on multiple platforms – Linux, Mac, Windows, IOS, Android, and potentially more
More about Ring:
Say Hello to Ring ― Ultimate Privacy and Control for your Voice, Video and Chat Communications
The need for efficient public distributed systems is becoming increasingly important as the influence of the Net giants centralizing information and communications more than ever is growing every day. This is a paradox since the Internet gives network nodes the unprecedented opportunity to exchange directly, without centralized processing point.
To address this issue, we developed OpenDHT — a free and open library implementing a distributed hash table and incorporating a number of important innovations. OpenDHT is at the heart of Ring, the decentralized communication system that we are also releasing today.
DHT (distributed hash table) is a class of distributed systems that provides access to a shared dictionary of key ➛ value pairs from any node of the network, and in which this data is distributed among the participants. Currently, the most popular DHT networks, such as Mainline DHT (BitTorrent), are used for peer to peer file sharing. On these networks, the key is the identifier of the torrent file — also called “Magnet link” — and the values are the IP addresses of the seeders, i.e. the clients sharing the torrent.
OpenDHT is a light and robust network project DHT in C++11 proposing a simple to use interface for application developers. Originally inspired by the DHT library developed by Juliusz Chroboczek and used, for example, by the BitTorrent client Transmission, OpenDHT includes a number of important innovations.
OpenDHT provides the ability to store any type of data — not just IP addresses — with a limit value of 64 KB. It has also a listening function (listen) enabling a node to be informed of changes in key values. Since we needed these crucial features for the Ring project, we wew pushed to create OpenDHT with the counterparty to make its protocol incompatible with the Mainline DHT network of BitTorrent.
The listen function is for example used in Ring to enable receiving calls or messages, even for computers behind NATs. In conjunction with the ICE technology, OpenDHT then allows the robust establishment of peer-to-peer connections.
OpenDHT is published on GitHub under the The GNU General Public License v3.0. Comments and patches are welcome. An early documentation is also available here.
OpenDHT is simple to use, thus reducing the cost and difficulty of developing applications that benefit from it. For example, starting a new node on local port 4222, and connecting to the network through a known node is as simple as these three lines of C++:
In the most popular type of DHT network (Kademlia) used by OpenDHT, each node (participant program) of the network has a unique identifier evenly distributed in the identifiers space — a 160-bit space in our case.
Similarly, each data stored on the network is characterized by an identifier which is its key. The keys are uniformly distributed in the same 160-bit space as the node identifiers. Multiple values can share the same key.
The binary operator XOR (⊕) is defined as the distance operator between key, or between keys and node IDs. To recap, the XOR result is true if both operands have different Boolean values. This implies that the XOR result of two 160-bit keys is the “binary distance” between these keys: A ⊕ A = 0 for every key A. For two distinct keys A and B with X = A ⊕ B, the number of zero bits at the beginning of X will be equal to the number of bits common to the beginning of A and B.
This interesting property offers the ability to partition each node’s routing table using a binary tree. In fact, each node maintains and updates a routing table including mainly the neighbouring nodes (in the sense of distance of the XOR operator introduced above).
A data element, that is to say a key-value pair (K, V), will be stored on the L nodes that are closest to key K (typically with L = 8). Any node knowing K will be able to find V by an iterative algorithm which will lead him to contact nodes whose identifiers are increasingly closer to K (Fig. 1).
Queries including the K key and the reply of each node include a list of other nodes known as closest to K. V value will be found in just O (log (N)) iterations — N representing the number of nodes on the network.
Just like the Internet, public DHT are inherently unreliable networks. They involve trusting many other programs randomly on the network to store data.
Instead of trying to make the protocol resistant and withstanding any type of malicious node, which would be illusive, the OpenDHT approach is to consider the network itself as untrustworthy and build over an optional cryptographic layer public key, using the PKCS infrastructure, and to verify the author and message integrity (signature) and encrypt the latter with public certificates published on the DHT network.
Knowing the identifier of the contact_id public key of a contact, storing an encrypted data for this contact on the DHT network is as simple as:
node.putEncrypted("my_key", contact_id, value);
The cryptography layer — or identity layer — then will transparently retrieve the certificate of the contact, use the public key to encrypt the data, and then store it on the network.
This layer will also transparently check the signature of signed data received. If the check fails, the data is not presented to the application. Similarly, only encrypted data that can be decrypted are passed to the application.
Ring implements these cryptographic operations to securely exchange invitations, initiation of calls and private messages. The network is therefore really used as a public meeting place.