Les plateformes et protocoles de chat existants présentent une partie ou la totalité des problèmes suivants :
Absence de confidentialité du profil et des contacts de l'utilisateur (confidentialité des métadonnées).
Aucune protection (ou seulement une protection optionnelle) des implémentations E2EE contre les attaques MITM via le fournisseur.
Messages non sollicités (spam et abus).
Absence de propriété et de protection des données.
Complexité d'utilisation de tous les protocoles non centralisés pour les utilisateurs non techniques.
La concentration de la communication dans un petit nombre de plateformes centralisées rend la résolution de ces problèmes assez difficile.
Solutions
Les différents protocoles proposés résolvent ces problèmes en faisant en sorte que les messages comme les contacts soit stockés exclusivement sur l'appareil client, tout en réduisant le rôle des serveurs à de simples relais de message qui ne nécessite que l'autorisation des messages envoyés dans les files d'attentes, mais qui NE nécessite PAS une authentification utilisateur - les message ne sont pas les seuls à être protégé, les métadonnées le sont aussi car l'utilisateur n'est pas lié à un identifiant - contrairement aux autres platformes.
Voir le livre blanc de SimpleX pour plus d'information sur les objectifs de la platforme et ses détails techniques.
Pourquoi utiliser SimpleX
SimpleX une approche unique en terme de confidentialité et de sécurité
Tout le monde devrait se soucier de la confidentialité et de la sécurité de ses communications - même une conversation lambda peut vous mettre en danger.
Protection complète de votre identité, profil, contacts et métadonnées
Contrairement aux autres platformes de messagerie, SimpleX ne lie pas d'identifiant à l'utilisateur - il n'y a pas besoin de numéro de télèphone (comme Signal ou WhatsApp), d'adresses basés sur des noms de domaines (comme les e-mails, XMPP ou Matrix), de noms d'utilisateurs (comme Telegram), ou de clés publiques ou même de nombres aléatoires pour identifié les utilisateurs - on ne sait même pas combiens de personnes utilise SimpleX.
Pour distribuer les messages au lieu d'utiliser des identifiants d'utilisateur que toute les autres platformes utilisent, SimpleX utilise des adresses unidirectionnelles (simplex) de files d'attentes de messages. Utiliser SimpleX c'est comme avoir une adresse e-mail différentes ou un numéro de télèphone différent par contact, sans les inconvenients qui viennent avec. Dans un futur proche les apps SimpleX changeront automatiquement les files d'attentes, déplacant les conversations d'un serveur à un autre, pour une meilleure confidentialité.
Cette approche protège la vie privé de la personne avec qui vous communiquez, elle est masquée des serveurs SimpleX et de n'importe quel autre observateur. Vous pouvez encore améliorer votre protection en configurant votre réseau pour qu'il passe via des réseaux superposé comme, par exemple Tor.
La meilleure protection contre le spam et les abus
Comme vous n'avez pas d'identifiant sur la plateforme SimpleX, vous ne pouvez pas être contacté, sauf si vous partagez un lien d'invitation unique ou une adresse d'utilisateur temporaire facultative. Même avec les adresses d'utilisateur facultatives, bien qu'elles puissent être utilisées pour envoyer des demandes de contact non sollicitées, vous pouvez les modifier ou les supprimer complètement sans perdre aucune de vos connexions.
Propriété, contrôle et sécurité totale de vos données
SimpleX stocke toutes les données de l'utilisateur sur les appareils clients, les messages ne sont conservés que temporairement sur les serveurs relais SimpleX jusqu'à leur réception.
Nous utilisons un format de base de données portable qui peut être utilisé sur tous les appareils pris en charge. Nous ajouterons bientôt la possibilité d'exporter la base de données de chat depuis l'application mobile afin qu'elle puisse être utilisée sur un autre appareil.
Contrairement aux serveurs des réseaux fédérés (e-mail, XMPP ou Matrix), les serveurs SimpleX ne stockent pas les comptes des utilisateurs, ils se contentent de relayer les messages aux destinataires, protégeant ainsi la vie privée des deux parties. Il n'y a aucun identifiant ou message chiffré en commun entre le trafic envoyé et reçu du serveur, grâce à la couche de chiffrement supplémentaire pour les messages délivrés. Par conséquent, si quelqu'un observe le trafic du serveur, il ne peut pas facilement déterminer qui communique avec qui (Voir le livre blanc de SimpleX pour les attaques connues de corrélation réseau).
Les utilisateurs sont maîtres du réseau SimpleX
Vous pouvez utiliser SimpleX avec vos propres serveurs et continuer à communiquer avec les personnes utilisant les serveurs préconfigurés dans les applications ou tout autre serveur SimpleX.
La plateforme SimpleX utilise un protocole ouvert et fournit un SDK pour créer des chatbot, permettant la mise en œuvre de services avec lesquels les utilisateurs peuvent interagir via les applications SimpleX Chat - nous sommes vraiment impatients de voir quels services SimpleX peuvent être créés.
Si vous envisagez de développer avec la plateforme SimpleX, que ce soit pour des services de chatbot pour les utilisateurs de l'application SimpleX ou pour intégrer la bibliothèque de chat SimpleX dans vos applications mobiles, n'hésitez pas à nous contacter pour tout conseil et assistance.
Comparaison avec d'autres protocoles
SimpleX chat
Signal et autres...
XMPP, Matrix
Protocoles P2P
Identifiants d'utilisateur nécessaire
Non = privé
Oui1
Oui2
Oui3
Risque d'attaque MITM
Non = securisé
Oui4
Oui
Oui
Dépendance au DNS
Non = résistant
Oui
Oui
Non
Un opérateur ou un réseau unique
Non = décentralisé
Oui
Non
Oui5
Attaque à l'échelle du réseau
Non = résistant
Oui
Oui2
Oui6
Généralement basé sur un numéro de téléphone, dans certains cas sur des noms d'utilisateur.
Basé sur le DNS.
Clé publique ou tout autre identifiant global unique.
Si les serveurs de l'opérateur sont compromis.
Si les réseaux P2P et les réseaux basés sur les crypto-monnaies sont distribués, ils ne sont pas décentralisés : ils fonctionnent comme un seul réseau, avec un seul espace de noms des adresses des utilisateurs.
Les réseaux P2P ont soit une autorité centrale, soit l'ensemble du réseau peut être compromis - voir la section suivante.
Il existe plusieurs protocoles et implémentations de chat/messagerie P2P qui visent à résoudre le problème de la protection de la vie privée et de la centralisation, mais ils ont leur propre série de problèmes qui les rendent moins fiables que la forme proposée, plus complexes à mettre en œuvre et à analyser et plus vulnérables aux attaques.
Les réseaux P2P utilisent une variante de DHT pour acheminer les messages/demandes à travers le réseau. Les implémentations du DHT ont des designs complexes qui doivent équilibrer la fiabilité, la garantie de livraison et la latence. La méthode proposée offre à la fois de meilleures garanties de livraison et une latence plus faible (le message est transmis plusieurs fois en parallèle, à travers un nœud à chaque fois, en utilisant des serveurs choisis par le destinataire, alors que dans les réseaux P2P, le message est transmis à travers O(log N) nœuds séquentiellement, en utilisant des nœuds choisis par un algorithme).
Le modèle proposé, contrairement à la plupart des réseaux P2P, ne comporte aucun identifiant global d'utilisateur, même temporaire.
Le P2P en lui-même ne résout pas le problème des attaques MITM, et la plupart des solutions existantes n'utilisent pas de messages hors bande pour l'échange initial de clés. La conception proposée utilise des messages hors bande ou, dans certains cas, des connexions sécurisées et fiables préexistantes pour l'échange initial de clés.
Les implémentations P2P peuvent être bloquées par certains fournisseurs d'accès à Internet (comme BitTorrent). Le modèle proposée est indépendant des moyens de transport : il peut fonctionner avec des protocoles web standard et les serveurs peuvent être déployés sur les mêmes domaines que les sites web.
Tous les réseaux P2P connus sont susceptibles d'être vulnérables à une attaque Sybil, car chaque nœud peut être découvert et le réseau fonctionne comme un tout. Les mesures connues pour réduire la probabilité de l'attaque Sybil nécessitent soit un composant centralisé, soit des preuves de travail coûteuses. Le modèle proposée, au contraire, ne permet pas de découvrir les serveurs - les serveurs ne sont pas connectés, ni connus les uns des autres, ni de tous les clients. Le réseau SimpleX est fragmenté et fonctionne comme de multiples connexions isolées. Cela rend impossible les attaques à l'échelle du réseau SimpleX - même si certains serveurs sont compromis, d'autres parties du réseau peuvent fonctionner normalement, et les clients affectés peuvent passer à l'utilisation d'autres serveurs sans perdre de contacts ou de messages.
Les réseaux P2P sont susceptibles d'être vulnérables aux attaques DRDoS. Dans la conception proposée, les clients ne relaient que le trafic provenant de connexions de confiance connues et ne peuvent pas être utilisés pour refléter et amplifier le trafic dans l'ensemble du réseau.
Address portability
Similarly to phone number portability (the ability of the customer to transfer the service to another provider without changing the number), the address portability means the ability of a communication service customer to change the service provider without changing the service address. Many federated networks support SRV records to provide address portability, but allowing service users to set up their own domains for the addresses is not as commonly supported by the available server and client software as for email.
Federated network
Federated network is provided by several entities that agree upon the standards and operate the network collectively. This allows the users to choose their provider, that will hold their account, their messaging history and contacts, and communicate with other providers' servers on behalf of the user. The examples are email, XMPP, Matrix and Mastodon.
The advantage of that design is that there is no single organization that all users depend on, and the standards are more difficult to change, unless it benefits all users. There are several disadvantages: 1) the innovation is slower, 2) each user account still depends on a single organization, and in most cases can't move to another provider without changing their network address – there is no address portability, 3) the security and privacy are inevitably worse than with the centralized networks.
The credential that allows proving something, e.g. the right to access some resource, without identifying the user. This credential can either be generated by a trusted party or by the user themselves and provided together with the request to create the resource. The first approach creates some centralized dependency in most cases. The second approach does not require any trust - this is used in SimpleX network to authorize access to the messaging queues.
In a wide sense, blockchain means a sequence of blocks of data, where each block contains a cryptographic hash of the previous block, thus providing integrity to the whole chain. Blockchains are used in many communication and information storage systems to provide integrity and immutability of the data. For example, BluRay disks use blockchain. SimpleX messaging queues also use blockchain - each message includes the hash of the previous message, to ensure the integrity – if any message is modified it will be detected by the recipient when the next message is received. Blockchains are a subset of Merkle directed acyclic graphs.
In a more narrow sense, particularly in media, blockchain is used to refer specifically to distributed ledger, where each record also includes the hash of the previous record, but the blocks have to be agreed by the participating peers using some consensus protocol.
Also known as Merkle DAG, a data structure based on a general graph structure where node contains the cryptographic hashes of the previous nodes that point to it. Merkle trees are a subset of Merkle DAGs - in this case each leaf contains a cryptographic hash of the parent.
This structure by design allows to verify the integrity of the whole structure by computing its hashes and comparing with the hashes included in the nodes, in the same way as with blockchain.
The motivation to use DAG in distributed environments instead of a simpler linear blockchain is to allow concurrent additions, when there is no requirement for a single order of added items. Merkle DAG is used, for example, in IPFS and will be used in decentralized SimpleX groups.
Also known as break-in recovery, it is the quality of the end-to-end encryption scheme allowing to recover security against a passive attacker who observes encrypted messages after compromising one (or both) of the parties. Also known as recovery from compromise or break-in recovery. Double-ratchet algorithm has this quality.
Double Ratchet algorithm provides perfect forward secrecy and post-compromise security. It is designed by Signal, and used in SimpleX Chat and many other secure messengers. Most experts consider it the state-of-the-art encryption protocol in message encryption.
Centralized network
Centralized networks are provided or controlled by a single entity. The examples are Threema, Signal, WhatsApp and Telegram. The advantage of that design is that the provider can innovate faster, and has a centralized approach to security. But the disadvantage is that the provider can change or discontinue the service, and leak, sell or disclose in some other way all users' data, including who they are connected with.
Content padding
Also known as content padding, it is the process of adding data to the beginning or the end of a message prior to encryption. Padding conceals the actual message size from any eavesdroppers. SimpleX has several encryption layers, and prior to each encryption the content is padded to a fixed size.
Decentralized network is often used to mean "the network based on decentralized blockchain". In its original meaning, decentralized network means that there is no central authority or any other point of centralization in the network, other than network protocols specification. The advantage of decentralized networks is that they are resilient to censorship and to the provider going out of business. The disadvantage is that they are often slower to innovate, and the security may be worse than with the centralized network.
The examples of decentralized networks are email, web, DNS, XMPP, Matrix, BitTorrent, etc. All these examples have a shared global application-level address space. Cryptocurrency blockchains not only have a shared address space, but also a shared state, so they are more centralized than email. Tor network also has a shared global address space, but also a central authority. SimpleX network does not have a shared application-level address space (it relies on the shared transport-level addresses - SMP relay hostnames or IP addresses), and it does not have any central authority or any shared state.
Defense in depth
Originally, it is a military strategy that seeks to delay rather than prevent the advance of an attacker, buying time and causing additional casualties by yielding space.
In information security, defense in depth represents the use of multiple computer security techniques to help mitigate the risk of one component of the defense being compromised or circumvented. An example could be anti-virus software installed on individual workstations when there is already virus protection on the firewalls and servers within the same environment.
SimpleX network applies defense in depth approach to security by having multiple layers for the communication security and privacy:
additional layer of end-to-end encryption for each messaging queue and another encryption layer of encryption from the server to the recipient inside TLS to prevent correlation by ciphertext,
TLS with only strong ciphers allowed,
mitigation of man-in-the-middle attack on client-server connection via server offline certificate verification,
mitigation of replay attacks via signing over transport channel binding,
multiple layers of message padding to reduce efficiency of traffic analysis,
mitigation of man-in-the-middle attack on client-client out-of-band channel when sending the invitation,
rotation of delivery queues to reduce efficiency of traffic analysis,
A communication system where only the communicating parties can read the messages. It is designed to protect message content from any potential eavesdroppers – telecom and Internet providers, malicious actors, and also the provider of the communication service.
End-to-end encryption requires agreeing cryptographic keys between the sender and the recipient in a way that no eavesdroppers can access the agreed keys. See key agreement protocol. This key exchange can be compromised via man-in-the-middle attack, particularly if key exchange happens via the same communication provider and no out-of-band channel is used to verify key exchange.
Also known as perfect forward secrecy, it is a feature of a key agreement protocol that ensures that session keys will not be compromised even if long-term secrets used in the session key exchange are compromised. Forward secrecy protects past sessions against future compromises of session or long-term keys.
Also known as break-in recovery, it is the quality of the end-to-end encryption scheme allowing to recover security against a passive attacker who observes encrypted messages after compromising one (or both) of the parties. Also known as recovery from compromise or break-in recovery. Double-ratchet algorithm has this quality.
Man-in-the-middle attack
The attack when the attacker secretly relays and possibly alters the communications between two parties who believe that they are directly communicating with each other.
This attack can be used to compromise end-to-end encryption by intercepting public keys during key exchange, substituting them with the attacker's keys, and then intercepting and re-encrypting all messages, without altering their content. With this attack, while the attacker does not change message content, but she can read the messages, while the communicating parties believe the messages are end-to-end encrypted.
Such attack is possible with any system that uses the same channel for key exchange as used to send messages - it includes almost all communication systems except SimpleX, where the initial public key is always passed out-of-band. Even with SimpleX, the attacker may intercept and substitute the key sent via another channel, gaining access to communication. This risk is substantially lower, as attacker does not know in advance which channel will be used to pass the key.
To mitigate such attack the communicating parties must verify the integrity of key exchange - SimpleX and many other messaging apps, e.g. Signal and WhatsApp, have the feature that allows it.
Also known as content padding, it is the process of adding data to the beginning or the end of a message prior to encryption. Padding conceals the actual message size from any eavesdroppers. SimpleX has several encryption layers, and prior to each encryption the content is padded to a fixed size.
Also known as key exchange, it is a process of agreeing cryptographic keys between the sender and the recipient(s) of the message. It is required for end-to-end encryption to work.
Also known as key exchange, it is a process of agreeing cryptographic keys between the sender and the recipient(s) of the message. It is required for end-to-end encryption to work.
The attack when the attacker secretly relays and possibly alters the communications between two parties who believe that they are directly communicating with each other.
This attack can be used to compromise end-to-end encryption by intercepting public keys during key exchange, substituting them with the attacker's keys, and then intercepting and re-encrypting all messages, without altering their content. With this attack, while the attacker does not change message content, but she can read the messages, while the communicating parties believe the messages are end-to-end encrypted.
Such attack is possible with any system that uses the same channel for key exchange as used to send messages - it includes almost all communication systems except SimpleX, where the initial public key is always passed out-of-band. Even with SimpleX, the attacker may intercept and substitute the key sent via another channel, gaining access to communication. This risk is substantially lower, as attacker does not know in advance which channel will be used to pass the key.
To mitigate such attack the communicating parties must verify the integrity of key exchange - SimpleX and many other messaging apps, e.g. Signal and WhatsApp, have the feature that allows it.
A technique for anonymous communication over a computer network that uses multiple layers of message encryption, analogous to the layers of an onion. The encrypted data is transmitted through a series of network nodes called "onion routers," each of which "peels" away a single layer, revealing the data's next destination. The sender remains anonymous because each intermediary knows only the location of the immediately preceding and following nodes.
Some elements of SimpleX network use similar ideas in their design - different addresses for the same resource used by different parties, and additional encryption layers. Currently though, SimpleX messaging protocol does not protect sender network address, as the relay server is chosen by the recipient. The delivery relays chosen by sender that are planned for the future would make SimpleX design closer to onion routing.
Nodes in the overlay network can be thought of as being connected by virtual or logical links, each of which corresponds to a path, perhaps through many physical links, in the underlying network. Tor, for example, is an overlay network on top of IP network, which in its turn is also an overlay network over some underlying physical network.
SimpleX Clients also form a network using SMP relays and IP or some other overlay network (e.g., Tor), to communicate with each other. SMP relays, on another hand, do not form a network.
The property of the cryptographic or communication system that allows the recipient of the message to prove to any third party that the sender identified by some cryptographic key sent the message. It is the opposite to repudiation. While in some context non-repudiation may be desirable (e.g., for contractually binding messages), in the context of private communications it may be undesirable.
The property of the cryptographic or communication system that allows the sender of the message to plausibly deny having sent the message, because while the recipient can verify that the message was sent by the sender, they cannot prove it to any third party - the recipient has a technical ability to forge the same encrypted message. This is an important quality of private communications, as it allows to have the conversation that can later be denied, similarly to having a private face-to-face conversation.
Generalizing the definition from NIST Digital Identity Guidelines, it is an opaque unguessable identifier generated by a service used to access a resource by only one party.
In the context of SimpleX network, these are the identifiers generated by SMP relays to access anonymous messaging queues, with a separate identifier (and access credential) for each accessing party: recipient, sender and and optional notifications subscriber. The same approach is used by XFTP relays to access file chunks, with separate identifiers (and access credentials) for sender and each recipient.
Peer-to-peer
Peer-to-peer (P2P) is the network architecture when participants have equal rights and communicate directly via a general purpose transport or overlay network. Unlike client-server architecture, all peers in a P2P network both provide and consume the resources. In the context of messaging, P2P architecture usually means that the messages are sent between peers, without user accounts or messages being stored on any servers. Examples are Tox, Briar, Cwtch and many others.
The advantage is that the participants do not depend on any servers. There are multiple downsides to that architecture, such as no asynchronous message delivery, the need for network-wide peer addresses, possibility of network-wide attacks, that are usually mitigated only by using a centralized authority. These disadvantages are avoided with proxied P2P architecture.
Network topology of the communication system when peers communicate via proxies that do not form the network themselves. Such design is used in Pond, that has a fixed home server for each user, and in SimpleX, that uses multiple relays providing temporary connections.
Perfect forward secrecy
Also known as perfect forward secrecy, it is a feature of a key agreement protocol that ensures that session keys will not be compromised even if long-term secrets used in the session key exchange are compromised. Forward secrecy protects past sessions against future compromises of session or long-term keys.
Any of the proposed cryptographic systems or algorithms that are thought to be secure against an attack by a quantum computer. It appears that as of 2023 there is no system or algorithm that is proven to be secure against such attacks, or even to be secure against attacks by massively parallel conventional computers, so a general recommendation is to use post-quantum cryptographic systems in combination with the traditional cryptographic systems.
Also known as break-in recovery, it is the quality of the end-to-end encryption scheme allowing to recover security against a passive attacker who observes encrypted messages after compromising one (or both) of the parties. Also known as recovery from compromise or break-in recovery. Double-ratchet algorithm has this quality.
User identity
In a communication system it refers to anything that uniquely identifies the users to the network. Depending on the communication network, it can be a phone number, email address, username, public key or a random opaque identifier. Most messaging networks rely on some form of user identity. SimpleX appears to be the only messaging network that does not rely on any kind of user identity - see this comparison.
