Frequently asked questions
Basics
Section titled “Basics”Does TalX need an account or a phone number?
Section titled “Does TalX need an account or a phone number?”No. On first launch the device generates a key pair – that is the entire sign-up. There is no registration, no e-mail address, no phone number and therefore no record held by a provider.
How do I find other users?
Section titled “How do I find other users?”You do not – and that is deliberate. There is no directory and no search. A contact only comes into existence when two devices deliberately exchange their public keys once: by QR code, NFC or a short code from a distance.
The practical side effect: strangers cannot message you.
What does TalX cost?
Section titled “What does TalX cost?”Nothing. No fees, no subscriptions, no advertising, no in-app purchases. If you want to support the development, you can do so voluntarily.
Which devices are supported?
Section titled “Which devices are supported?”Android 8 and newer, 64-bit. No iOS, no desktop, no web – an iOS version is on the roadmap. Google Play Services are required for short-range delivery.
Delivery
Section titled “Delivery”Does TalX really work without the internet?
Section titled “Does TalX really work without the internet?”Yes – between devices in range. Over Bluetooth and Wi-Fi Direct two devices talk to each other directly. On the same Wi-Fi they find each other via mDNS and deliver over a direct connection. Voice and video calls on a local network also work with no server at all.
Only when none of those paths carries does internet brokering come into play.
Why does my message say “waiting for delivery”?
Section titled “Why does my message say “waiting for delivery”?”Because the recipient has not confirmed it yet. TalX deliberately only sets the tick then – not when you press send. Until then the message sits in the encrypted queue and is retried on every new connection.
In groups the tick only arrives once all members have confirmed. A permanently offline member therefore keeps the message waiting longer. That is more honest, not worse.
What does the small symbol on a message mean?
Section titled “What does the small symbol on a message mean?”The transport path actually used: Bluetooth, Wi-Fi, internet, relay or Sidelink. On messages you sent it appears only with the confirmation, because before that the path is not settled.
Do messages arrive while the app is closed?
Section titled “Do messages arrive while the app is closed?”Yes, as long as “stay active in the background” is switched on. A foreground service keeps reception and delivery alive; Android requires a permanent notification for this.
Honestly: some manufacturers’ aggressive battery optimisation can kill the service anyway. The profile therefore has a button leading straight to the system battery list.
Why does the service not start by itself after a reboot?
Section titled “Why does the service not start by itself after a reboot?”From Android 15 onwards, starting automatically after boot is not permitted for this kind of service. The service therefore starts when the app is first opened.
What exactly does “online” mean?
Section titled “What exactly does “online” mean?”Reachable right now – within short range or connected through the brokering. For this the app sends a tiny sign of life to its contacts every 45 seconds, but only if a connection exists at all. If there is none, there is no presence information either.
Encryption
Section titled “Encryption”What exactly is encrypted?
Section titled “What exactly is encrypted?”Everything that leaves the device. Messages, media, profile and status updates, presence signals, call signals and even the connection details for calls. No transport holds a key.
On the device: the database via SQLCipher, the attachments via AES-256-GCM, and the keys for both behind a hardware-wrapped master secret.
What is “post-quantum protection” and do I need it?
Section titled “What is “post-quantum protection” and do I need it?”An adversary could record encrypted traffic today and decrypt it years later with a sufficiently large quantum computer. Against that, TalX mixes an ML-KEM-1024 secret into the root key in addition to the classical method. The classical method stays in place – the post-quantum share comes on top and cannot make anything worse.
The chat header shows whether it is active, being set up, or whether the app on the other side is too old for it.
What is the safety number and do I have to check it?
Section titled “What is the safety number and do I have to check it?”It proves that nobody was in between when you connected. Tap the shield symbol in the chat, compare the numbers with the other person over a second channel – in person or by phone, not in the same chat – and mark them as verified.
Have to: no. Should: yes, if you are serious about it. Without this step you are relying on the pairing process itself not having been tampered with.
TalX warns me about a key change. Am I being intercepted?
Section titled “TalX warns me about a key change. Am I being intercepted?”Usually not. The most common cause is that the other side reinstalled the app or restored a backup. It can also be an interception attempt – hence the warning. Compare the safety number again in that case.
Can the operator of the brokering read my messages?
Section titled “Can the operator of the brokering read my messages?”No. They receive nothing but ciphertext and can neither read it nor alter it undetected.
They do see which identifiers communicate with each other and when. That is unavoidable with server-based delivery. Anyone who wants to rule that out too uses TalX purely offline or runs the brokering themselves.
Has TalX been security-audited?
Section titled “Has TalX been security-audited?”Internally yes, externally no. There are extensive internal cryptography and full audits with documented findings, regression tests and an ongoing field test on real hardware. An independent external audit is outstanding and tracked as open finding F-07.
For communication that a life depends on, Signal is the more dependable choice. All the details: audit findings and limits.
Privacy
Section titled “Privacy”What data does TalX collect about me?
Section titled “What data does TalX collect about me?”None. TalX has no analytics, no crash reports to third parties, no advertising identifier and no user account. There is no place where your data could come together. Full breakdown: privacy policy.
How do I delete all my data?
Section titled “How do I delete all my data?”There is no account to delete. How to remove messages, contacts, all app data and the backup is set out step by step under delete your data.
Do my voice messages leave the device for transcription?
Section titled “Do my voice messages leave the device for transcription?”No. Recognition runs with an offline engine directly on the device. The audio is never transmitted. Only the language model comes from the network, once.
The transcript is a purely local artefact: not part of the encryption, not transmitted, and deleted along with the message.
And when translating?
Section titled “And when translating?”The same. The translator runs on the device. A cloud translator would receive the plaintext of every translated message – exactly what end-to-end encryption exists to prevent. Only the language model comes from the network.
Why does TalX need location permissions?
Section titled “Why does TalX need location permissions?”On older Android versions (up to 12L) the system required them for Bluetooth device discovery – not because TalX wants to know your location. From Android 13 there is a dedicated “nearby devices” permission, and the Bluetooth scan is explicitly flagged as not for deriving location. TalX does not collect, store or transmit location data.
Media and features
Section titled “Media and features”How large may attachments be?
Section titled “How large may attachments be?”Up to 100 MB in a one-to-one chat. 50 MB in groups and towards older app versions.
What happens to “view once” media?
Section titled “What happens to “view once” media?”The recipient sees only a placeholder. Tapping opens the medium exactly once, full screen – and it can still be saved to the gallery at that moment – after which the file is deleted. The same applies to your own sent copy.
It is an agreement between two cooperating apps, not a technical guarantee: photographing the screen is always possible.
Can I block someone?
Section titled “Can I block someone?”Yes, via contact info → block. Nothing is accepted from that person afterwards: no messages, no attachments, no calls – it does not even ring – no profile or presence details, not even in shared groups. The chat history is kept; to delete it, long-press in the chat list as before.
Two things deliberately keep running: delivery confirmations and the presence heartbeat. If both stopped at once, the other side would know immediately that they had been blocked – and might switch to another channel. Details: connecting contacts.
Does the other person notice that I blocked them?
Section titled “Does the other person notice that I blocked them?”Not immediately. Their messages are still confirmed and your device keeps sending signs of life – from the outside it looks as though everything arrives. What stays away are replies. That is not a guarantee: anyone who gets nothing back for long enough can work it out.
Can someone get around a block by reinstalling?
Section titled “Can someone get around a block by reinstalling?”No. A block applies to the person, not the key – it survives a re-pairing even when the other side turns up with a fresh key.
Can I delete or edit messages?
Section titled “Can I delete or edit messages?”Both. Deleting removes the message for everyone and leaves a placeholder. Editing works on text messages for up to five minutes after sending and leaves the note “edited”.
Are there disappearing messages with a timer?
Section titled “Are there disappearing messages with a timer?”No.
How many languages does the interface speak?
Section titled “How many languages does the interface speak?”91, fully – including notifications, presence information with correct plural forms and system notices in the chat. If a translation is missing, English steps in.
Groups
Section titled “Groups”Who may do what in a group?
Section titled “Who may do what in a group?”The creator may rename it, set the group picture, manage members, appoint moderators, transfer ownership and delete the group for everyone. Moderators may remove members. The creator cannot be removed by anyone and cannot leave the group – they transfer ownership first, or delete it.
How is that enforced without a server?
Section titled “How is that enforced without a server?”On receipt, every device checks for itself whether the sender holds the role for this change. A tampered app can send claims – the other devices do not believe them.
Why are there no very large groups?
Section titled “Why are there no very large groups?”Because every message is encrypted separately for every member and delivered separately. That is the price of serverlessness, and it scales for households and teams, not for hundreds of participants.
Backup and devices
Section titled “Backup and devices”Where is my backup?
Section titled “Where is my backup?”As a single encrypted blob in the private app folder of your own Google account. TalX can see nothing there but its own folder. Every backup overwrites the previous one.
What do I need to restore it?
Section titled “What do I need to restore it?”Two factors: your passphrase and a TOTP code or biometrics. Both are mandatory, even on the device that created the backup.
I forgot my passphrase.
Section titled “I forgot my passphrase.”Then the backup is lost. There is no second key and no recovery by the project – nobody but you can decrypt the blob. That is the price of the fact that nobody else can either.
Can I use TalX on two devices?
Section titled “Can I use TalX on two devices?”Yes, with a linking code. Afterwards both devices are the same identity. Both have to be Android.
What happens if I lose my phone?
Section titled “What happens if I lose my phone?”The data on it stays encrypted and cannot be unwrapped without that device’s secure element. On a new device you restore from the backup – for which you need the passphrase and the second factor. Without a backup, the chat history and contacts are gone; messages live exclusively on the devices.
Problems
Section titled “Problems”No nearby device is found.
Section titled “No nearby device is found.”- Bluetooth and Wi-Fi have to be switched on on both devices.
- The “nearby devices” permission has to be granted. If it was permanently denied: system settings → apps → TalX → permissions.
- Both devices need Google Play Services.
- If the “offline connections” switch is off, TalX deliberately does not search.
- The connect screen shows live what the problem is.
Messages arrive late.
Section titled “Messages arrive late.”Usually the manufacturer’s battery optimisation is killing the background service. Exclude TalX from it – the profile has a button for that.
One conversation stops delivering.
Section titled “One conversation stops delivering.”TalX normally heals session disruptions by itself. If that does not help, the safety-number dialogue offers “reset the encrypted session”. Afterwards it is best to compare the safety number again.