Tella features
All of the following features are available to all users as soon as they download Tella. They do not require any connection to a server or any special set up.
App lock
When installing Tella, the user has to select a lock 🔒 to encrypt and decrypt the content of the app.
- On Android, the user can select a pattern, PIN, or password.
- On iOS, the user can select a PIN or password.
Without this lock, it is not possible to open Tella.
If the user loses their lock, it is not possible to regain access to Tella and the files stored inside the app. The user has to uninstall and reinstall Tella, and all files will be lost. We recommend users saving their locks somewhere safe, like a password manager.🔒🔑🚪
Learn more about Tella Locks in our video tutorial
Background encryption
Tella encrypts files in the background so that users can continue performing actions (take more photos or videos, import more files, etc) while files are being encrypted. Users can see ongoing activities that are taking place in the background in a Background activity tray that's accessible from the Tella homescreen, by tapping on the "notifications" icon (🔔) on the top left.
While files are being encrypted, Tella displays an orange marker on the notifications icon. If the user opens the background activity tray while some files are being encrypted, they will see the list of files in the queue and the encryption progress.
If the user hard exit Tella (for example by using Quick Exit or minimizing the app) while files are being encrypted in the background, those will be lost.
If verification mode is turned on, background encryption is automatically disabled to make sure that all file metadata is captured at the same time as the photo, video, or audio file is saved.
Backup files
Tella stores all the information locally in your phone. If you delete your files (for example using quick delete or if you uninstall Tella), your files cannot be restored unless you have backed them up outside of your Tella Vault.
We offer several alternatives to backup files, so you can safely delete files from Tella and import those back in, but the backup process is manual, for the moment. Please contact us if you have questions.
All exports outside of Tella's encrypted vault (to a connected server or to your phone) will be unencrypted. The only method for sharing files that transfer files directly to another encrypted vault is Nearby Sharing.
Backup files to another phone or computer
Using Nearby Sharing you can transfer files directly to another Tella vault, either in another phone or to a computer that's in physical proximity. Files are shared and store encrypted in the other Tella. If you backup to another phone you can use Nearby Sharing again to restore the files to your Tella.
For the moment Tella Desktop can only receive files.
Backup files to a cloud
Some individuals use commercial clouds (Google Drive, Dropbox, Nextcloud) as a backup system for their Tella data. However, we advise using this feature with caution:
- Automatic backups to any server are not currently available. They need to be made manually as submissions to each of the servers.
- Files on the server will be accessible to anyone with server access.
You can continue reading about Server Connections and how organizations use Tella here.
Lock timeout configuration
By default Tella will lock immediately every time the user exits the app or your phone’s screen turns off. If you’d like to change this setting, the user can do so by going to
Settings ⚙️ > Security > Lock Timeout.
The available options are 1 minute, 5 minutes, 30 minutes and 1 hour. ⏱️
Please use this feature carefully as if Tella is unlocked the data would be unprotected and anyone who enters Tella will be able to see all information there.
When the camera or the audio recorder are open, Tella won’t lock
Learn more about Tella Additional Security Features in our video tutorial
Camera silent mode
By default Tella has camera silent mode disabled. By going to Settings ⚙️ > Security > Camera silent mode, it is possible to turn off the camera shutter sound to draw less attention when taking photos. 📷🔇
Learn more about Tella Additional Security Features in our video tutorial
Screen security
By default Tella blocks screenshots, screen recordings inside Tella and hides the screen preview in the list of recent apps 📱🔒. It is possible to disable this security feature if the users need to take screenshots or screen recordings, or to mirror Tella to a computer for a presentation, by going to Settings ⚙️ > Security > Screen security.
On iOS screen security only blocks screen recordings inside Tella and blocks the screen in the list of recent apps, but it’s not possible to disable screenshots or screen recordings.
Learn more about Tella Additional Security Features in our video tutorial
Restrict unlocking attempts
By going to Settings ⚙️ > Security > Delete after Failed Unlock, the user can decide how many failed unlock attempts are allowed before everything inside Tella is deleted.
By default, this setting is Off, which means unlock attempts are not restricted and data won't be deleted. The user can choose to restrict unlocking attempts to 5, 10, or 20. If they choose any of these options, they can also select whether to display a visual indicator on the unlock screen 3 attempts before the specified number (3 attempts remaining, 2 attempts remaining, etc.), or to show no visual indicator at all.
After the specified number of failed attempts, all files, connections, and everything in Tella get deleted, and the user will go back to the "freshly installed" app state.
The Restrict unlocking attempts feature cannot be enabled if Calculator camouflage is enabled.
While this security setting prevents brute force unlocking attempts to enter Tella, it should be used with caution, as there is no way to restore the content of Tella once the maximum number of failed unlocking attempts is reached.
Edit Media
We are in the process of adding the ability to edit media files directly within Tella's encrypted container, so users don't longer need to export their files outside Tella for editing those.
| Media Type | Feature | Tella Android | Tella iOS | Tella FOSS |
|---|---|---|---|---|
| Image | Crop | ✔️ | ✔️ | ✔️ |
| Image | Rotate | ✔️ | ✔️ | ✔️ |
| Image | Flip | ✔️ | Not yet | ✔️ |
| Image | Auto-zoom | ✔️ | ✔️ | ✔️ |
| Video | Trim | Not yet | ✔️ | Not yet |
| Video | Rotate | Not yet | ✔️ | Not yet |
| Audio | Trim | Not yet | ✔️ | Not yet |
Users can edit a picture by going to More > Edit from the Images folder or by tapping the Edit button on the top right while viewing image you have on Tella.
- Rotate: Use the Rotate button at the bottom of the screen to rotate the image counter-clock wise.
- Crop: Drap the corners of the white canvas to crop the picture.
- Auto-zoom: The image will automatically zoom in and out depending on the selected canvas, to avoid loosing image quality.
- Flip: Use the flip buttons to mirror the image horizontally or vertically.
When edits are done, users can press the orange check on the top right of the edit screen. The edited file will be saved as a copy of the original file in the same folder.
Users can edit videos or audio recordings:
- In any folder, next to the file to be edited, by tapping on ⁝ > Edit.
- While listening to an audio recording or watching a video in Tella, by tapping the Edit button in the top right corner.
Current editing options include:
- Trim: Move the vertical orange lines to select the new start and end point of your audio or video.
- Rotate: Use the Rotate button on the top right of the screen to rotate the video counter-clock wise.
Use the Play button at the bottom of the screen to listen to the audio or the Cancel button to start over. When you are done editing the file, use the orange scissors ✂️ icon in the top-right corner to save the trimmed audio or video. The edited file will be saved as a copy of the original file in the same folder.
Encryption
All files stored inside Tella are encrypted. Without the app lock, it is impossible to decrypt and access any of the files stored in Tella. 🔒🔐
Upon installing the app, the user decides which lock method they would like to use. For Android, the user can use a six-point pattern, a PIN, or a password. For iOS, they can use a PIN or a password. The app cannot be opened without the lock.
Even if the device is plugged into a computer and all the device's data is extracted to be analyzed, all Tella content and data will look like gibberish and will be useless. Unlocking the app by entering the correct lock is the only way to decrypt, and therefore read, the content stored in Tella.
If the user’s lock is too weak, an adversary may be able to guess it and open the app on the phone; or the data could be extracted and a computer could brute-force the encryption key and decrypt the data.
If the user forgets their lock, there is no way of gaining access to the app and retrieving its content
Learn more about Locks and Encryption in our video tutorial
Technnical details about encryption can be found on the Security and Privacy section.
File management
Tella allows users to manage files and folders in a similar way they would do on a computer. All files and folders are encrypted and only accessible within Tella. 📂📝
In Tella, users can:
- Store any file, including photos 📷, videos 🎥, audio files 🎧, and documents 📝.
- In the All Files folder:
- Create folders and subfolders.
- Move files into folders and from one folder to another.
- Export files to their device. Once saved on their device outside of Tella, files are no longer encrypted and can be accessed by anyone searching the device.
- Save the verification information of a file as a CSV file, stored in the same folder as the original file.
- Import files from their device. Files are automatically encrypted when imported into Tella.
Importing files from the device file system into Tella makes a copy of the files into Tella. Tella will ask if you want to keep or delete the original file from your phone when importing. If you choose to keep the original file, they will be present on the device, outside of Tella and unencrypted. 🔒
Feedback
There are several options for Tella users to contact the Tella team in order to suggest improvements, report bugs and issues and request support. Inside Tella there are 2 alternatives:
-
Email:
- Navigate to Settings > About and Help > Contact us to find the email address.
- Users can email the Tella team using their preferred email app.
-
In-App Feedback Form:
- Go to Settings > Feedback to enable an in-app feedback form.
- This allows users to share feedback with the Tella team anonymously.
To ensure user privacy and anonymity, only essential data is transmitted to our Feedback server through HTTPS POST requests. Logs containing user information (IP address, date and time, and user-agent) are automatically deleted weekly.
On the Feedback server database, we only store a copy of the text sent by users in the feedback form and which platform it came from (Android or iOS).
The only information that we will receive is the content that users specifially add on the feedback form. If users are requesting support or want us to follow up with them, they should provide a secure way for us to contact them.
Import files from device
The user can import files into Tella to keep them secured by using the import feature. They can import files by going to the Add ( + ) button on either All files, Images, Video, Audio or Documents depending on the type of file they wish to import and then Import from device 📥. A prompt will appear asking the user if they would like to keep or delete the original file from their phone memory. The imported files will be kept secured at Tella.
Learn more about Collecting Evidence and Sharing data in our video tutorials.
Preserve metadata when importing
On Settings > Security users have the option to Preserve or delete the file's metadata when importing Photos and Videos to Tella. EXIF metadata of files migth include data about when the file was created, camera settings or location of the device.
Privacy preserving analytics (opt-in)
Android users can opt-in to share analytics to improve Tella. All information is anonymous, agregated and can never be linked to individual usres. For technical information about what system do we use and what metrics to we collect, visit the Analytics section of the Security and Privacy page.
Open files in Tella
Images, videos, PDFs and audios can be visualized inside Tella. 📱📄
Camouflage
On Tella Android, it is possible to camouflage Tella in two ways:
- Users can change the name and icon of the app, to make it look like another app like a game or weather app. 🎮🌦️
- Users can hide Tella behind a fully functional calculator. In order to open Tella, the user must input their PIN into the calculator followed by = . The Calculator camouflage is only possible if the user uses a PIN lock. It is not possible to camouflage Tella as a Calculator if pattern or password is used. 🔢🔒
At this time, due to restrictions on the Apple App Store, Tella for iOS does not support the camouflaging features that are available on Tella Android.
The name "Tella" and its icon will remain visible in the Android settings. This means that camouflage will not protect against an individual actively looking for Tella on the phone or conducting an in-depth analysis of the device. 🔒👀
The Calculator camouflage feature cannot be enabled if the Restrict unlock attempts feature is on.
Learn more about Camouflaging Tella in our video tutorial.
Homescreen customization
By default Tella's home screen organizes files by type: 📷 images, 🎥 videos, 🎧 audio, 📄 documents, and other files. It also provides an All files section where all files can be accessed. For more information see File Management section.
For convenience and ease of access, it is also possible to customize the home screen to also show shortcuts to one or more of the following:
- Recent files, to quickly open the newest files in Tella 💼
- Favorite forms, for users connected to an ODK server 📝
- Favorite templates, for users connected to an Uwazi server 📋
This configuration can be found in Settings > General.
Quick delete
A Quick Delete button allows users, in just a few seconds, to delete sensitive data within Tella. Quick delete can be configured on Settings > Security > Quick delete, where the user can choose to enable a sliding button on the home screen to quickly delete information from Tella in emergency situations. If enabled, the user can choose exactly what gets deleted when the feature is used. The available options are:
- Delete files: Deletes all files stored in Tella 🗑️ . This is the default option.
- Delete Connections: Deletes all your connections, and all data asociated with them (including drafts, outbox and submitted reports). Visit the For Organizations page to discover the available server connections 📝
- Delete Tella: Deletes the app and all the data it contains. It triggers a message asking if the user wants to uninstall Tella as well ❌.
The Delete Tella option might not be available on some Android phones due to technical limitations. We are working on a fix for this issue. For iOS it is not possible to programmatically delete an app, so the Delete Tella option is not available.
Before triggering Quick Delete, consider backing up you files outside of Tella, to avoid loosing them.
Quick exit
By clicking the exit button on Tella’s home screen right top corner, Android users can quickly close and lock the app in case of emergency. While having the lock timeout set to “immediately” means that the app already locks when the user exits, using the Quick Exit button adds an extra layer of security and assurance that the app will be fully closed and locked 🔒
On iOS, it is not possible to shut down an app from inside the app itself. Tapping the quick exit button instead locks the app.
Verification mode
When activated, every time a user takes a photo or a video, or records audio, Tella automatically captures verification information (file metadata). This verification information can be used to corroborate evidence, cross-check with other facts known about the event or about the area where it was captured.
To turn it on, go to Settings ⚙️ > General > Verification mode. Tella will ask for permission to access the device's location. Verification information is only collected for files captured with Tella's camera and audio recorder while verification mode is on. It is not collected for files imported from the device.
Verification information can identify the user and their device (for example their location, IP addresses or device ID). Only share it if doing so will not put you or others at risk.
Viewing verification information
To see the verification information of a file, open the file's options menu (⋮), either from a folder or while viewing the file, and select Verification information. While viewing the file, it can also be opened by tapping the verification information button (🛡️) in the top bar. This option is only available for files that have verification information.
Saving and sharing verification information
Verification information is stored as a CSV file, with one column per field. It can be opened with any spreadsheet app (like Excel, Google Sheets or LibreOffice). The CSV file has the same name as the original file (for example, photo.jpg → photo.csv).
- Save it inside Tella: on the Verification information screen, tap Save as CSV. The CSV is saved, encrypted, in the same folder as the original file, and can be attached to reports and connections like any other file. The CSV stays linked to the original file: if the original file is deleted, its CSV is deleted too.
- Share it or export it to the device: when sharing or exporting files that have verification information, Tella asks whether to include it. Choose Share files + verification information to include the CSV, or Share files only to leave it out. When exporting to the device with verification information, Tella also saves the CSV inside Tella, if it wasn't saved before.
What information is collected
File 📂
| Field | What it means | Where it comes from |
|---|---|---|
| File name | The file's name in Tella. | Tella. |
| File path | The folder where the file is stored in Tella, for example /Evidence/March, or / if it is not in a folder. | Tella's folder structure. |
| File hash | A unique alphanumeric sequence (a SHA-256 hash) that identifies the file's exact content. | Calculated by Tella from the original, unencrypted file when it is saved. |
| File created | The date and time the file was saved in Tella. | Tella. |
| File modified | The date and time the file was last renamed or moved in Tella. | Tella. |
Device 📱
| Field | What it means | Where it comes from |
|---|---|---|
| Manufacturer | The name of the device manufacturer. | Android system information. |
| Hardware | The manufacturer and model of the device. | Android system information. |
| Device ID | A unique identifier of the device. It stays the same if Tella is deleted and reinstalled, and it is different for Tella and Tella FOSS on the same device. | Provided by Android (Android ID). |
| Screen size | The size of the screen's diagonal, in inches. | Calculated from the screen's resolution and pixel density, so it may differ slightly from the manufacturer's specification. |
| Wi-Fi MAC (WiFi MAC) | The hardware identifier of the device's Wi-Fi connector. | Android. On recent Android versions apps can no longer access this value, so this field can be empty. |
| Language | The language used by Tella: the language selected in Tella's settings or, if none was selected, the language of the device. | Tella and Android language settings. |
| Locale | The country or region the device is set to, as a country code. | Android region settings. |
Network 📶
Permissions: Cell info requires location permission (precise or approximate). Wi-Fi info requires precise location permission and location turned on. Without them, these fields are not available.
| Field | What it means | Where it comes from |
|---|---|---|
| Connection status (Network) | Whether the device had a network connection. | Android connectivity information. |
| Network type | Whether the device was connected through Wi-Fi or mobile data. | Android connectivity information. |
| Data type | If the device was connected through mobile data, the type of mobile network (for example, LTE or 3G). Empty when connected through Wi-Fi. | Android telephony information. |
| IPv4 / IPv6 | The IP addresses assigned to the device's network connections. These are usually local addresses (for example, assigned by the Wi-Fi router or a VPN), not the public IP address seen on the internet. | The device's network interfaces. |
| Cell info (Cells) | The identifiers (country code, network code and cell ID) of the cell towers detected by the device. | Android telephony information. |
| Wi-Fi info (WiFis) | The names of the Wi-Fi networks detected near the device. | A Wi-Fi scan made by Tella. |
Location 📍
Permissions: requires precise location permission and location turned on. Without them, these fields are not available.
| Field | What it means | Where it comes from |
|---|---|---|
| Location provider | How the location was obtained: GPS (satellites) or network (Wi-Fi and cell towers, usually less accurate). | Android location services. |
| Latitude / Longitude | The coordinates of the device, in degrees. | Android location services. |
| Altitude | The altitude of the device, in meters. | Android location services. |
| Accuracy (Location accuracy) | The estimated accuracy of the location, in meters. The smaller the number, the more precise the location. | Android location services. |
| Location speed | The speed at which the device was moving, in meters per second. | Android location services. |
| Timestamp of GPS reading (Location timestamp) | The date and time the location was measured. | Android location services. |
Other 🌡️
| Field | What it means | Where it comes from |
|---|---|---|
| Ambient temperature | The temperature around the device. | The device's temperature sensor. |
| Light | The level of light around the device, in lux. | The device's light sensor. |
Some fields may not be available depending on the device, the permissions that you have chosen to give Tella, the device settings and the location circumstances. For example, the location may not be available indoors, and many devices don't have a temperature sensor.
On the Verification information screen, fields without a value show Not Available. In the CSV, they are left empty, and if there is no location, cell or Wi-Fi information, those columns are not included.
If you need help to better understand Verification Mode, feel free to contact us 😊
Connecting to servers
Users can collect data directly in Tella, keep the data protected within the app, and connect to a server to securely send the data to a server. This feature is frequently used by organizations who centralize the data collected by volunteers or activist on the ground. These people collect information using Tella on their phones and then send it to their organizations. Previous Tella deployments where on-the-ground users collect data and send it to an organization's server have ranged from 1 to 2,000 users. 📲 📡.
Currently the servers that can be connected to Tella are:
You can read more about servers and how organizations have been using this feature here.
Learn more about Connecting to Servers in our video tutorials.
Nearby Sharing
Users can share files directly from Tella’s encrypted vault to another Tella encrypted vault in the same physical location using Nearby Sharing . After a quick connection tutorial, the two devices establish a secure link, and files are transferred encrypted from one device to the other. Nearby Sharing is independent of the internet connection status: it works online or offline.
This feature is available on Tella Android, Tella iOS, and Tella Desktop.
Share button
To share information with other apps, users can select the file or files they want to share and press the Share button. Tella will prompt the list of available apps on the phone and users can choose the app they want to share the file(s) with.
If any of the selected files has verification information, Tella asks whether to include it as a CSV file or to share only the files.
Tella will share the files unencrypted and the history of exchanged files might be visible on the app you used. We recommend using disappearing messages or deleting the messages after the other person receives them when using messaging apps (for example WhatsApp or Signal).
Camera (photos and videos)
Tella offers a built-in camera where you can take photos and videos. All media collected inside Tella will not be available outside of it, as all files get encrypted as soon as they are taken. Files can only be accessed inside Tella, using the lock to open the app. Photos and videos won’t appear on the phone Gallery. In Tella, photos and videos will have a default name, but users can rename those using the Rename button. Files can also be organized in folders. 📷
The camera offers the possibility to change the resolution of videos before recording in order to save space: the lower the resolution, the less space the video takes, but also the lower the quality of the video. 🎥 💾
The camera also offers the following options:
- Flash: choose between on, off, or auto.
- Grid: shows a grid overlay to help frame and align photos and videos.
- Zoom: pinch to zoom in or out before taking a photo or recording a video.
- Switch camera: switch between the front and back cameras.
Select video resolution
You can easily choose your desired video resolution on Tella by accessing the video recording screen and tapping on the Settings button. The available options include:
- Highest possible resolution
- High resolution (1080p)
- Medium resolution (720p)
- Low resolution (480p)
Video resolution refers to the number of pixels in each frame of the video. Higher resolutions, such as 1080p or 720p, result in sharper and more detailed videos. However, keep in mind that higher resolution videos also have larger file sizes, which may require more storage space on your device.
It's important to note that selecting video resolution is currently only supported on Android devices.
Audio Recorder
Tella has a built-in audio recorder. All audio recorded inside Tella will not be available outside of it, as all files get encrypted as soon as they are taken. Audio files can only be accessed inside Tella, using the lock to open the app. Recordings will not appear on the phone’s Voice Recording app or file system. In Tella, audio files will have a default name, but users can rename those using the Rename button. Audio recordings can also be organized in folders. 🎤 🎧
The audio recorder allows users to pause the recording and restart it as needed, keeping all the information on the same file. Users see how much space they have available while recording, to ensure they will not be out of space while recording. 📈 💾
Offline data collection
Once Tella is installed and configured on the phone, it doesn't need an internet connection to collect data. 📲 An internet connection is only needed to share files through other apps or through Connections. 🌐 If users have a server connected, once the forms or templates are downloaded to the phone, all data collected will be stored on the outbox tab and they can upload it to the server once they connect to the internet. 📩