A full AI assistant — writing, images, web search, memory, file uploads — where every conversation is end-to-end encrypted on your device, so the company says it cannot read your chats, train on them, hand them to partners, or produce anything but scrambled text in response to a subpoena. Built by Moxie Marlinspike, the cryptographer who created Signal. Free to start with no credit card; the encryption and private inference designs are written up publicly and the code is open source so the claims can be checked.
Why I recommend it: This is the one to reach for when you are about to type something into an AI that you would not want read back to you — money trouble, health, a manager, a visa problem. Two honest things. It is free to start, which is not the same as free forever, so read the plan page before you rely on it. And encryption protects the message, not your judgment: anything you paste in that belongs to an employer or a client is still their information, whoever can or cannot read it.
A free 2025 paper by Mallory Knodel, Sunoo Park, Kyunghyun Cho and colleagues at NYU and Cornell examining whether AI assistants and end-to-end encryption can honestly coexist. It covers two cases — putting an AI assistant inside an encrypted app, and training models on encrypted data — sets out where each breaks the security promise encryption makes, works through the legal consequences when a provider keeps saying "end-to-end encrypted" anyway, and ends with concrete recommendations on default settings, consent and what providers may truthfully claim.
Why I recommend it: Read the recommendations section even if you skip the cryptography. It gives you the exact questions to put to any product that advertises both an AI helper and private messaging — where does the processing happen, what is the default, and what were you actually asked to agree to. Two flags: it is posted to a preprint archive, so it has not been through journal peer review, and the authors published plain-language summaries on the NYU DeTaIL Lab blog and Tech Policy Press if the full paper is heavy going.
