Open Privacy assigned one developer to carry out and oversee most of the development of both apps. A second developer provided additional coding time and review, and we were fortunate to have recently hired a staff designer as well who was able to assist with the project's design, documentation and logo. We were able to leverage our open-source libraries from another project (Cwtch), including our Go-Qt cross-platform build pipeline and recently released QML widget/theme library to rapidly create a working companion application to the web app.
In order to move quickly through testing and initial deployment, we began by implementing a simple web form that used straightforward encryption with common libraries to implement the architecture we had settled on. Namely, we created a PHP app that used libsodium's secret_box for public-key encryption.
Setup begins with the desktop application, which handles key generation and, later, decryption. A chosen person (or group) from the organization obtains the application (from our website, although this may be subject to change) and runs it on the computer where the long-term secret/private key will be stored. A single button press is all it takes to generate a new cryptographic keypair, consisting of a public key file which can be uploaded to the web app, and a private key file which should be kept offline and backed up to a USB drive or other appropriate private backup location. We strongly caution against putting private key files on cloud storage.
From there, the organization's representative sent us the public key to upload to the web form (along with the form's questions to be asked, as we did not even have an online form editor at the time!). A public link could then be handed out to members, who submitted the form from their own devices. When submissions were received, HTTP POST data was serialized, encrypted with the uploaded public key, and appended to a submissions log for later bulk downloading.
Around this time, we also began discussing our efforts on social media. This resulted in other organizations with similar needs and requirements reaching out to us to express interest in LockBox. After some internal discussion about the best way to address these requests, it was decided that LockBox would become a full-fledged Open Privacy application with support for multiple users/forms, a more polished user experience, and potentially even a hosted option for those who trust Open Privacy enough with their ciphertexts.
While the organization's mutual aid fund was in full swing, we continued development on the prototype to make it a more professional-looking app that meets Open Privacy's standards.
The LockBox web app was upgraded from raw PHP to using the Twig template engine (the same one created for the Symfony PHP framework). User accounts and support for multiple custom forms was added, as was basic form editor functionality.
Also, thanks to some volunteer work from our board member (todo: permission/citation) who is working to set up LockBox for another community organization, we now support running the web app via popular containerization service Docker. :)
The LockBox desktop app was made using Open Privacy's Cwtch stack; native Go code with Qt bindings to handle a UI defined via QML. As mentioned above, we recently released Cwtch's widgets as a standalone QML library called Opaque, and this enabled us to rapidly create an on-brand and professional-looking application with the flexibility of easily writing the encryption code using libsodium bindings for Go, a language the entire team is comfortable working with.
To help reduce friction in the setup process, we also added the ability for the desktop app to auto-upload public keys to the appropriate user and form on a specified (arbitrary) hosting server.