On November 30, 2023, Localization Lab hosted a Tella Demonstration and Ask-Me-Anything event. The project developer had the opportunity to showcase their tool, the changes they have made, what brought about the creation of the application, and the use cases in various contexts in so far as internet freedom and digital rights are concerned. The space discussed best practices for the use of the tool and provided space for participants to ask questions and provide feedback they may have on existing features of the tool.
The Tella team through their product manager, Caro Hadad, shared how the Tella App (developed by the Horizontal team) works and how it is being used in various contexts and organizations in different countries to collect data, document violations, protect information from tampering and subsequently how organizations can use the information to make informed decisions that make an impact on the work they are doing.
Horizontal is an organization that supports frontline defenders, activists, and journalists through digital security and tool development.
Caro explained how Tella is already being used in different countries to collect data during elections both online and offline, document human rights violations, and collect information for research, advocacy, and transitional justice. Some of the use cases she highlighted included:
Election monitoring in Nigeria, Serbia, Belarus
Human rights documentation in Myanmar
The investigation of mass atrocities in South Sudan
The gross violations of environmental and land rights in the Brazilian Amazon
Use by Individuals on a day-to-day basis in their work
Digital security trainers who provide support to people on the ground
Digital Security trainers providing support to journalists in Southern Africa who have found the tool very useful
In the course of their work, Caro stated that they had received feedback from users of the tool which included:
Activists facing harassment and violence
Devices being searched and confiscated
Servers being attacked to destroy evidence
How Tella works
Caro indicated that users can take pictures/videos and record audio with the app. The files then get encrypted and sent to a server. These images/videos/audio do not appear in the phone's gallery -- the only way to access the files is by opening the app using a password. Even if someone has physical access to the user's phone, or to the source files, they can't open any of the files without that password.
The Camouflage feature:
Tella can be camouflaged in the user's phone by changing the name and the icon of the app to something unsuspicious (e.g., selfie cam, weather app)
A more secure way to camouflage is if you have a numerical password, you can camouflage the app into a fully functional calculator. If you type in your Tella password into the calculator, it will open the app.
Chat feedback: I was wondering if Tella might get found if someone decided to brute force and check out all the apps on a phone, but this way they would never know the calculator had another app underneath. Very cool!
Caro also explained that there have been a few more added features to the app in the last couple of months in the form of auto-reporting and auto-deleting files. For example, if you are at a protest and you don't have time to go to reports, attach the file, etc. and send these directly to the server. A point to note here is Tella only needs an internet connection in the moment of sending the files or a report to the server. All data collection can be done offline. There's an option to set it up so that the server automatically tries to reconnect if you lose internet connection.
The team is also working to integrate Proof mode soon - to strengthen the capacity to present the data in international courts of law.
The Tella app is available for Android and iOS.
We also had some time to answer questions from participants during the Q&A segment. Below are some of the questions asked by community members;
Q: Is the camouflage feature not available on iOS?
C: Not yet, because of a technical difficulty. If you submit an app to the iOS store you cannot change its icon or name, so users can't use the feature once they download the app. The Horizontal team is working on a workaround for this (probably submitting the app as a calculator with a calculator icon).
Q: Just to understand the threat model here: if bad actors have the device for an extensive period (like one week, or even longer, as is usual in the case of device confiscations), and the bad actors are knowingly looking for Tella, could they identify it by other means, even if "Camouflage" is enabled? (for example by the size of the app, containing encrypted media)
C: Strongly agree with your points. If one's threat model is very high, there will certainly be data forensics going on the phone to find any data stored. It is not possible to dodge that as far as I know since Android/iOS just show data usage by app. You can find more info about the security limitations here.
Q: Is the server open source as well?
C: Yes, it is. Please contact me at caro@wearehorizontal.org for more information. Alternatively, you can take a look at the code on our GitHub
Q: Is the server self-hostable meaning we could have personal copies of the server as with Docker?
C: Yes, correct. You can find technical documentation about how to install your private Tella Web server here: https://tella-app.org/tella-web. If you need support from our technical team to decide if Tella Web is the right server for your use case, please contact us.
Q: When the auto-delete feature is turned on, does the photo/video always get instantly deleted, or is there a way to set a small delay (in case the photo/video was not good)?
C: The app deletes files as soon as it's confirmed that they moved to the server. There is a "quick delete" function where the user can select what gets deleted when the delete button is triggered if you don't want to immediately delete files. The Horizontal team is working on a feature where the user will be able to set up the amount of time that passes between creating the file and deletion.
Q: Who is Tella for? How do you go about the design of it? Share with us the journey how you developed the tool.
C: We reached out to users that they know use Tella and asked them whether an idea makes sense for their context. Since the alpha version, the end-user is at the center. The team hosts community calls (the first Wednesday of every month) where they brainstorm with the community about pressing issues, language accessibility, features, etc. Link to the calls: https://tella-app.org/community-meetings. There is a page on the Tella website where users can reach out to the Tella team and ask questions and provide feedback: https://tella-app.org/contact-us
Q: I’m curious how you go about user research and how that contributes to your design process. For example, are you doing in-person sessions with people/partners who represent groups of interest? Do you have people going into the field to get direct feedback from the communities or partner orgs that you work with, etc.?
C: Yes, besides what I explained above, sometimes we also conduct sessions with people or partners of groups of interest. For example, this month we are running usability tests on our documentation platform.
Q: Who are the partners you work with on the legal side of this?
C: I'm not sure if with "legal" you mean if we work with external organizations that audit our work. If that's the case, yes. Some of the types of audits we have are as shown below:
We don't have specific partners that advise our users on legal aspects of the human rights documentation process because each country and topic has its specific characteristics. Depending on the case, if a user or group asks us to recommend security or legal experts and we happen to know someone, we would recommend them!
Q: It has been documented before that Apple abides by government requests and may remove your app from access in an oppressive country. What are the proposed solutions for this?
C: We offer alternative ways to download Tella Android:
See here a video on how to manually install Tella from the installable file.
Find options to find and download Tella from outside the stores.
A version of Tella is also available in the F-Droid store
For iOS, currently, we don't have similar alternatives because it's not so easy to manually install an app that's not on the App Store. But please contact us if you have a specific case in mind or if you have ideas or recommendations on how to make Tella more accessible for iOS users.
Q: Do you need to create an account to use Tella?
C: No, you do not need an account. Take a look at the FAQ section on our website for further information.
Q: Even after auto-deletion, would the recorded files be traceable from the device reports to the server, i.e. does this give the user plausible deniability that they have recorded sensitive materials?
C: To the best of my knowledge auto-delete triggers a full deletion of the files on Tella and also removes any records on the phone that this report has been sent to the server. So, I think this would give users plausible deniability that they have recorded these materials
Q: When you mention the encryption at rest all the files are encrypted. If someone fully mirrors your phone, in that scenario is the data still encrypted or in an unencrypted format? I suppose when you export data from Tella it is encrypted but is the data still in encrypted format if someone copies your entire phone storage?
C: If you export a file from Tella to your device, that new file won't be encrypted. Files that are within the Tella vault will be encrypted. If someone copies the phone memory (including Tella's internal memory) those files will be encrypted as well.
Q: Here in this link: https://tella-app.org/security-and-privacy it's mentioned the data cannot be read using a computer but on the same page it says it can be read under "File Management".
C: Yes, that's what I mentioned above: if a file gets exported outside of the Tella vault (for example it is saved on the device memory (outside of Tella) or shared to a third-party app) the file will be unencrypted because it could not be read by other people if we were to share it encrypted. But none of these actions happen without user involvement. The user will need to explicitly take their files outside of Tella for those to be unencrypted or accessible by other people without the Tella lock. Please ping us to better explain this over a call if needed!
Q: Is there a limit to how much data can be stored on Tella?
C: Tella itself doesn't have a specific limit. This is determined by the device storage space.
Q: Is it not stored in the cloud too? How do collaborative features like sharing reports work if everything is saved locally on the device?
C: Yes, reports and all server connections require an internet connection. The files are saved locally on the device, but to share those with others, the internet is needed. We are planning to implement phone-to-phone transfer, but that would be for 2024.
Q: Did the Tella team check out the Signal library for the file encryption? Which encryption does Tella use for file encryption?
C: I don't have details top of my mind about what library is used for encryption. The code is open source and can be found here. We can also set up a meeting with the Android devs or forward to them any specific technical questions .
Q: Is file compression available on Tella? If yes, how does it work?
C: It is not available for photos, but is available for videos. You can choose a resolution to record your video in.
Q: How easy is it to create your server?
C: Email Caro so she can share more detailed instructions and explain the process.
Q: Technically, I'm wondering if it is possible for someone with enough knowledge to create an "evil twin" of the server to simulate it and intercept uploaded data. I believe this might be possible with the help of DNS poisoning.
C: I'm not a security expert but yes, I think this might be possible. Do you have any specific ideas or advice on how we could address this issue? please contact us to brainstorm about that.
For those who want to know more about Tella, please see the following Tella resources below:
Tella’s user-facing documentation platform
Video Tutorials (with subtitles in English, Spanish, Arabic, and Swahili) and getting-started guides for Android and iOS
Contact page, in case you want to reach out directly or to stay in touch by subscribing to the Tella newsletter.
If you are interested in helping localize Tella into your local language, please reach out to either Chido (chido@localizationlab.org) or Dianne (dianne@localizationlab.org) for onboarding and orientation.