Sealist

Sealist 🦭

A browser extension offering seamless E2E encryption for Todoist. Basically, this cutie seals your tasks and comments only for you to see.

Background

What Todoist Already Does

See Todoist Security Policy.

• All user data is encrypted at rest in their production database.
• Encryption is keyed by a master key held by Todoist.

• Master key compromise or misuse.
• A court order or legal compulsion.
• A breach of the live app stack - prod read access means plaintext access, employee or attacker alike.
• A future policy change on who gets to read your content.
• Cross-border data-sharing pressures.

Move the trust boundary off Todoist's server and onto the user's browser. Encrypt before task leaves, decrypt on the way back. Todoist's servers see opaque ciphertext. Plaintext only ever exists inside the browser client while the extension is Unsealed.

We want to provide a similar model to Mailvelope/FlowCrypt which layer PGP onto Gmail, but without requiring users setting PGP keys.

We should not make Todoist that much worse to use :p. The crypto should be conservative and audited. The codebase must be small enough to read. The shortcomings must be documented honestly.

Non Goals

We are not trying to defeat:

• Malware running on the user's machine with arbitrary access (extension memory, screenshots, key loggers).
• A malicious extension installed by the user with the same host_permissions reading our injected DOM. Extensions are isolated from each other's in-memory state and storage, but not from a malicious extension reading the page we both render to.
• A user picking a low-entropy password. We gate on password complexity and employ a memory-hard KDF to make the offline attack as expensive as we honestly can, but a determined adversary wins against low-entropy passwords if one would pass the checks.

License

Copyright (C) 2026 yaspltbr

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.