diff --git a/src/pages/posts/2026/encrypted_XMPP.md b/src/pages/posts/2026/encrypted_XMPP.md index 51e5b41..909e317 100644 --- a/src/pages/posts/2026/encrypted_XMPP.md +++ b/src/pages/posts/2026/encrypted_XMPP.md @@ -11,346 +11,392 @@ description: 'Secure and private messaging with XMPP and OMEMO encryption.' --- -# End-to-End Encryption in XMPP with OMEMO +# End-to-End Encryption in XMPP with OMEMO -I find it funny that twenty years ago I was already trying -to get people to switch to XMPP. +I find it funny that twenty years ago I was already trying +to get people to switch to XMPP. -For a long time, ICQ was extremely popular around me, +For a long time, ICQ was extremely popular around me, but the proprietary messenger kept breaking things for people using alternative clients, which was quite annoying. -After yet another round of this pointless battle -I realized clearly that I prefer protocols over services. +After yet another round of this pointless battle +I realized clearly that I prefer protocols over services. -I didn't have much success back then, -but fortunately, XMPP (and I hope I have too) +I didn’t have much success back then, +but fortunately, XMPP (and I hope I have too) has continued moving forward over the past two decades. -It has developed slowly, sometimes awkwardly, but steadily. +It has developed slowly, sometimes awkwardly, but steadily. -Here, I won't talk about why XMPP is great or how it works. +Here, I won’t talk about why XMPP is great or how it works. You can check this guide -(one of many) and I'd rather not write another one. -In this post, I want to focus specifically on end-to-end encryption -and the practical aspects of using it. +(one of many) and I’d rather not write another one. +In this post, +I want to focus specifically on end-to-end encryption +and the practical aspects of using it. ## Short Glossary -**End-to-end encryption** is a way to keep your chats truly private.
-Only you and the person you're messaging can read the messages. -Not even the server owner has the keys needed to decrypt or modify them. +**End-to-end encryption** is a way +to keep your chats truly private.
+Only you and the person you’re messaging can read the messages. +Not even the server owner has the keys +needed to decrypt or modify them. -**XMPP** is an extensible protocol for instant messaging. -It's open, decentralized, and mature. +**XMPP** is an extensible protocol for instant messaging. +It’s open, decentralized, and mature. -**OMEMO** is a widely supported XMPP Extension Protocol (XEP) for secure multi-client end-to-end encryption. You can read more about -it on a dedicated page by Daniel Gultsch. + target='_blank'>dedicated page by Daniel Gultsch. -**Client**, in this post, -means a specific instance of an XMPP application on a user device. +**Client**, in this post, +means a specific instance +of an XMPP application on a user device.
OMEMO-related documentation uses the term Device, -but I find it potentially confusing: -in practice, a single physical device can run multiple independent clients. +but I find it potentially confusing: +in practice, a single physical device +can run multiple independent clients. ## Basic Concepts -This section introduces some basics of end-to-end encryption. +This section introduces some basics of end-to-end encryption. -If you're already familiar with the concepts and terminology, +If you’re already familiar with the concepts and terminology, you can skip ahead to how end-to-end encryption affects the XMPP user experience -or jump straight to the step-by-step workflow I personally use. + href='#practical-aspects-of-omemo-and-xmpp'>how end-to-end encryption + affects the XMPP user experience, +or jump straight to the step-by-step workflow I personally use. ### Trade-offs Between Safety and Convenience Unfortunately, things that are truly secure are rarely convenient. -They often require some initial efforts and a bit of ongoing attention. +They often require some initial efforts +and a bit of ongoing attention. -Telegram, which used to be a benchmark for messenger usability +Telegram, which used to be a benchmark for messenger usability before its long dive into enshitification, really draws the line between convenience and security. Regular chats are easy and flexible, -but "secret" chats come with a full set of limitations: -they're one-on-one only, -can't be synced to another device, -aren't available on desktop at all, -and so on. +but “secret” chats come with a full set of limitations: +they’re one-on-one only, +can’t be synced to another device, +aren’t available on desktop at all, +and so on. -All commercial so-called "secure" messengers, like Signal or WhatsApp, -end up with pretty similar limitations, -because it's tricky to make end-to-end encrypted chats +All commercial so-called “secure” messengers, like Signal or WhatsApp, +end up with pretty similar limitations, +because it’s tricky to make end-to-end encrypted chats work the way users expect. -Luckily, protocols and cryptography don't care about -convenience or user expectations. -Many XMPP clients let you do almost anything you're trying to do. -Sometimes it's clunky and unintuitive, -sometimes it's the kind of freedom that lets you shoot yourself in the foot. -At the end of the day, you'd better understand what you're doing. +Luckily, protocols and cryptography don’t care about +convenience or user expectations. +Many XMPP clients let you do almost anything you’re trying to do. +Sometimes it’s clunky and unintuitive, +sometimes it’s the kind of freedom +that lets you shoot yourself in the foot. +At the end of the day, you’d better understand what you’re doing. -It might sound messy, but for that price, XMPP actually -gives you a lot of handy features: +It might sound messy, but for that price, XMPP actually +gives you a lot of handy features: your chats are secured with Signal-grade end-to-end encryption, -and you can use as many devices as you want, -all at the same time, -without being tied to any proprietary service. +and you can use as many devices as you want, +all at the same time, +without being tied to any proprietary service. -In general, the XMPP experience today -could be described as a "WhatsApp with benefits and frictions". -It's kinda ironic, considering that WhatsApp's protocol -is actually based on XMPP, but incompatibly altered and defederated. +In general, the XMPP experience today +could be described as a “WhatsApp with benefits and frictions”. +It’s kinda ironic, considering that WhatsApp’s protocol +is actually based on XMPP, but incompatibly altered and defederated. ### Keys, Fingerprints and Trust -OMEMO is based on the - +OMEMO is based on the Double Ratchet Algorithm. While the internal details are quite interesting, -for practical purposes it's enough to know that +for practical purposes it’s enough to know that each client stores some cryptographic keys -and can derive a hash from them, commonly called a fingerprint. +and can derive a hash from them, commonly called a fingerprint. -Keys are usually managed automatically by the XMPP client, -and in normal use you should never need to handle them manually. -In fact, you probably don't even need to know what they look like. +Keys are usually managed automatically by the XMPP client, +and in normal use you should never need to handle them manually. +In fact, you probably don’t even need to know what they look like. -A fingerprint lets you identify a specific client of your contact -and verify that it hasn't been spoofed. -Fingerprints for an account are not secret: -clients publish their own fingerprints to the XMPP server -and automatically receive the fingerprints of others. -Only fingerprints you explicitly mark as trusted are relevant. +A fingerprint lets you identify +a specific client of your contact +and verify that it hasn’t been spoofed. +Fingerprints for an account are not secret: +clients publish their own fingerprints to the XMPP server +and automatically receive the fingerprints of others. +Only fingerprints you explicitly mark as trusted are relevant. -In an ideal scenario, the contact should confirm in person -or through an already trusted and secure communication channel -that the fingerprint belongs to their device, -and only then you mark it as trusted. -In most XMPP clients this is simply done by ticking a checkbox -or by scanning a QR code. +In an ideal scenario, the contact should confirm in person +or through an already trusted and secure communication channel +that the fingerprint belongs to their device, +and only then you mark it as trusted. +In most XMPP clients this is simply done +by ticking a checkbox +or by scanning a QR code. -The list of trusted fingerprints is used at the moment a message is sent. -Behind the scenes, OMEMO performs a certain amount of key management, -and only the clients that are present in the trusted list -at the time of encryption will be able to decrypt the message later. +The list of trusted fingerprints +is used at the moment a message is sent. +Behind the scenes, +OMEMO performs a certain amount of key management, +and only the clients that are present in the trusted list +at the time of encryption +will be able to decrypt the message later. -It's important to understand that trust cannot be applied retroactively: -it's not possible to "extend" trust to new clients -after a message has already been encrypted and sent. +It’s important to understand +that trust cannot be applied retroactively: +it’s not possible to “extend” trust to new clients +after a message has already been encrypted and sent. -## Practical Aspects of OMEMO and XMPP +## Practical Aspects of OMEMO and XMPP ### Chat History -In theory, XMPP supports server-side message history storage via +In theory, XMPP supports server-side message history storage via **XEP-0313: Message Archive Management**. -In practice, support for this XEP, -as well as retention policies and message lifetime, -depends on the specific server. +In practice, support for this XEP, +as well as retention policies and message lifetime, +depends on the specific server. You should never assume that all conversations are stored -indefinitely by default. -From a practical standpoint, -the server-side MAM archive is better considered a cache: -it can help you handle recent messages after a short period offline -or synchronize conversations across multiple devices. +indefinitely by default. +From a practical standpoint, +the server-side MAM archive is better considered a cache: +it can help you handle recent messages after a short period offline +or synchronize conversations across multiple devices. -At the end of the day, keeping your chat history is your responsibility, -and this is a good place to apply a local-first approach. +At the end of the day, +keeping your chat history is your responsibility, +and this is a good place to apply a local-first approach. ### Synchronisation -Seamless switching between clients is handled by +Seamless switching between clients is handled by **XEP-0280: Message Carbons**. Before its introduction, only incoming messages were synced between devices, while your own outgoing messages were not. -Protocol-level mirroring of your own messages -is a rather non-obvious feature :D +Protocol-level mirroring of your own messages +is a rather non-obvious feature :D -It's important to note that with end-to-end encryption, -the concept of trusted fingerprints also applies to your own clients. -For seamless synchronisation of outgoing messages, -all your clients must trust each other's fingerprints. -A new client, -or an old one that was not trusted at the time messages were sent, -will receive the full history from MAM but will not be able to decrypt it. +It’s important to note that with end-to-end encryption, +the concept of trusted fingerprints also applies to your own clients. +For seamless synchronisation of outgoing messages, +all your clients must trust each other’s fingerprints. +A new client, +or an old one that was not trusted +at the time messages were sent, +will receive the full history from MAM +but will not be able to decrypt it.
Yes, even your own messages. -In theory, re-encrypting messages on already trusted clients -could solve this issue, but no XMPP client implements it yet. -So in practice you may need to manually resend -some data to a new device. +In theory, re-encrypting messages on already trusted clients +could solve this issue, but no XMPP client implements it yet. +So in practice you may need to manually resend +some data to a new device. ### Message Correction -It's worth keeping in mind that -features that seem simple and straightforward at first glance, -such as message editing and deletion, -actually rely on client-side implementation +It’s worth keeping in mind that +features that seem simple and straightforward at first glance, +such as message editing and deletion, +actually rely on client-side implementation and may not behave for your recipient the way you expect. -They're fine to use and are well supported in some clients, -but you shouldn't rely on them to hide anything. +They’re fine to use and are well supported in some clients, +but you shouldn’t rely on them to hide anything. ### Maintenance -OMEMO was designed as a set-it-and-forget-it solution, -and it mostly succeeds in that goal. -If you have a basic understanding of how the protocol works -and check in online from time to time, -there shouldn't be any surprises. +OMEMO was designed as a set-it-and-forget-it solution, +and it mostly succeeds in that goal. +If you have a basic understanding of how the protocol works +and check in online from time to time, +there shouldn’t be any surprises. -All maintenance comes down to making regular backups +All maintenance comes down to making regular backups and notifying your contacts -when fingerprints are added or no longer valid -so they can keep their trust list up to date. +when fingerprints are added or no longer valid +so they can keep their trust list up to date. ## Step-by-Step Guide -Let's say I have a XMPP account, `me@some.server`, -and a few devices: a phone, a laptop, and a desktop computer. -First I'll describe my mindset at a high level, -then I'll add some notes about specific clients. +Let’s say I have a XMPP account, `me@some.server`, +and a few devices: +a phone, a laptop, and a desktop computer. +First I’ll describe my mindset at a high level, +then I’ll add some notes about specific clients. ### Client Roles -On the one hand, I have my phone. -It's almost always with me and almost always online. -That's where I keep the full chat history and get real-time notifications. +On the one hand, I have my phone. +It’s almost always with me and almost always online. +That’s where I keep the full chat history +and get real-time notifications. -On the other hand, I have a couple of desktop applications. -I only open them when I need to discuss something using my keyboard -or share some text between devices. -I like to think of them as satellite clients. +On the other hand, I have a couple of desktop applications. +I only open them +when I need to discuss something using my keyboard +or share some text between devices. +I like to think of them as satellite clients. ### Before the Start -First, enable OMEMO encryption on every client if it isn't enabled by default. +First, enable OMEMO encryption +on every client if it isn’t enabled by default. -The next step is to add all clients to the trust list on each device: -my phone should trust all my computers, -and my computers should trust each other as well as my phone. +The next step is to add +all clients to the trust list on each device: +my phone should trust all my computers, +and my computers should trust each other +as well as my phone. -Fingerprints do not have to be secret, so they can be published on -your website or even on social media profiles. -Here is my page with the fingerprints, for example: +Fingerprints do not have to be secret, +so they can be published on +your website or even on social media profiles. +Here is my page with the fingerprints, for example:
https://oddsquat.org/about/keys/ -### Start the Conversation in Person +### Start the Conversation in Person -Let's say I meet Alice, -we start talking, and then decide to continue the conversation online. +Let’s say I meet Alice, +we start talking, +and then decide to continue the conversation online. -I open a special QR code on my phone, and Alice scans it with her client. -This QR code already contains the fingerprints of all my devices, -so no extra steps are needed on her phone. -After that, I do the same and scan her QR code as well. +I open a special QR code on my phone, +and Alice scans it with her client. +This QR code already contains +the fingerprints of all my devices, +so no extra steps are needed on her phone. +After that, I do the same +and scan her QR code as well. -Later at home, I manually mark her devices as trusted on my computers -using the trusted list on my phone, and she does the same. +Later at home, +I manually mark her devices as trusted on my computers +using the trusted list on my phone, and she does the same. -Now we are both sure that it is really us in the conversation, -and that all messages will be available on all our devices and only on them. +Now we are both sure +that it is really us in the conversation, +and that all messages will be available +on all our devices and only on them. ### Start the Conversation Online -Let's say Bob and I start discussing something -on a forum or in the Fediverse, -and then decide to continue the discussion on XMPP. +Let’s say Bob and I start discussing something +on a forum or in the Fediverse, +and then decide to continue the discussion on XMPP. -Bob starts the chat. I trust the first device he messages me from, -and then we exchange fingerprints for our other devices, if we have any. -This approach is called TOFU (Trust On First Use). +Bob starts the chat. +I trust the first device he messages me from, +and then we exchange fingerprints for our other devices, +if we have any. +This approach is called TOFU (Trust On First Use). -Bob can confirm it's really me using my page with fingerprints. -I can confirm it's really him by asking him to send his fingerprints -in a private message on the same forum or via email. +Bob can confirm it’s really me using my page with fingerprints. +I can confirm it’s really him +by asking him to send his fingerprints +in a private message on the same forum or via email. -Ideally, Bob also has a public page with his fingerprints. -That way, we can both independently verify -that we are who we say we are. +Ideally, Bob also has a public page with his fingerprints. +That way, we can both independently verify +that we are who we say we are. -### New or Lost Devices +### New or Lost Devices -If I start using a new device or install another client application, -the first thing I do is add it to the list of trusted clients -on my existing devices. +If I start using a new device +or install another client application, +the first thing I do is add it to the list +of trusted clients on my existing devices. -If I lose one of my devices or delete any private keys, -the first thing I do is remove the corresponding client -from the trusted list on my other devices. +If I lose one of my devices +or delete any private keys, +the first thing I do is remove the corresponding client +from the trusted list on my other devices. -Once I've updated all my personal lists, -I should inform my contacts about changes via trusted channels. +Once I’ve updated all my personal lists, +I should inform my contacts about changes via trusted channels. -I can simply ask Alice to scan my new QR code the next time we meet, -and send Bob a message introducing my new client or letting him know -that the lost device is no longer trusted -and that no real messages will ever come from it again. +I can simply ask Alice to scan +my new QR code the next time we meet, +and send Bob a message introducing +my new client or letting him know +that the lost device is no longer trusted +and that no real messages will ever come from it again. ## Client Applications -This section describes how OMEMO is used in specific client applications -that I personally use. +This section describes +how OMEMO is used in specific client applications +that I personally use. ### Conversations and Forks -Conversations is a modern, fully featured chat application for Android. -It supports everything a messaging app should support: -chats, voice calls, video calls, and sharing files of any kind. +Conversations is a modern, +fully featured chat application for Android. +It supports everything a messaging app should support: +chats, voice calls, video calls, and sharing files of any kind. -There are several forks of it where the UI or UX may differ, +There are several forks of it where +the UI or UX may differ, but the core features work exactly the same. -I personally use Monocles Chat. +I personally use Monocles Chat. -On the Contact Details screen (including your own account), -you can see a list of published fingerprints -and manually mark them as trusted or revoke trust. +On the Contact Details screen (including your own account), +you can see a list of published fingerprints +and manually mark them as trusted or revoke trust. -To simplify all these routine operations, a QR-code-based system is used: -you can show your own QR code or scan other people's codes +To simplify all these routine operations, +a QR-code-based system is used: +you can show your own QR code or scan other people’s codes directly from the main screen. -This makes device verification during in-person meetings simple and effortless. +This makes device verification during in-person meetings +simple and effortless. ### Dino -Dino is a lightweight GTK-based GUI client. +Dino is a lightweight GTK-based GUI client. -It can be considered a fully functional one, +It can be considered a fully functional one, although some non-essential features are still not implemented. For example, -it is not possible to clear local chat history using built-in methods :D +it is not possible to clear local chat history +using built-in methods :D -Trust and untrust decisions can be easily managed -in the Encryption tab of the Conversation Details window. +Trust and untrust decisions can be easily managed +in the Encryption tab of the Conversation Details window. -It is important to note that, by default, Dino is configured -to automatically trust new fingerprints. -I recommend disabling this feature. +It is important to note that, +by default, Dino is configured +to automatically trust new fingerprints. +I recommend disabling this feature. ### Profanity -Profanity is a powerful TUI client -where everything is controlled through a built-in command system. +Profanity is a powerful TUI client +where everything is controlled through a built-in command system. -If you somehow intend to use it, -you can find a small cheat sheet for the `/omemo` command below. -However, I strongly recommend reading the full documentation. +If you somehow intend to use it, +you can find a small cheat sheet for the `/omemo` command below. +However, I strongly recommend reading the full documentation. -- Generate a key and add your other clients: +- Generate a key and add your other clients: ```text /omemo gen /omemo trust me@some.server some-cool-fingerprint-01 @@ -358,41 +404,42 @@ However, I strongly recommend reading the full documentation. /omemo qrcode ``` -- View the list of your own or someone else's fingerprints: +- View the list of your own or someone else’s fingerprints: ```text /omemo fingerprint me@some.server /omemo fingerprint alice@another.server ``` - Trusted ones will be marked as `trusted`. + Trusted ones will be marked as `trusted`. -- Start an encrypted conversation: +- Start an encrypted conversation: ```text /omemo start alice@another.server ``` -- Add fingerprints to the trusted list: +- Add fingerprints to the trusted list: ```text /omemo trust alice@another.server some-cool-fingerprint-02 /omemo trust alice@another.server some-cool-fingerprint-03 /omemo trust bob@another.server some-cool-fingerprint-04 ``` -- Revoke trust for a specific client: +- Revoke trust for a specific client: ```text /omemo untrust alice@another.server some-cool-fingerprint-02 ``` ## Late Disclaimer -This post was originally intended as a collection of answers to questions -I had when I first started using XMPP with OMEMO. +This post was originally intended +as a collection of answers to questions +I had when I first started using XMPP with OMEMO. -It isn't meant to be exhaustive or formal, -but rather to clarify the practical side of things -and reduce that initial feeling of being lost +It isn’t meant to be exhaustive or formal, +but rather to clarify the practical side of things +and reduce that initial feeling of being lost when you keep running into -"The message was not encrypted for this device" +“The message was not encrypted for this device” over and over again. -From now on, I hope you won't encounter errors like this -or any other issues with end-to-end encryption in XMPP. +From now on, I hope you won’t encounter errors like this +or any other issues with end-to-end encryption in XMPP.