The idea is to have a secure offline way of encrypting messages and data on your device using HPKE and a selection of encryption key types, including Secure Enclave bound ones, to protect the data in transit or at rest. As in, encrypt and optionally sign, send by any means, and only have your designated recipient (or yourself) read it. Messages can be shared as deep links for one click decryption with automated quick key probing. Files - same, but via import from anywhere.
No permission requests, no analytics, no accounts, no ads, no subscriptions, absolutely zero online requests. No "make your own crypto" silly things. Everything is using the iOS bundled CryptoKit. Hence the tiny size of it.
Authenticated mode also supports passwords in addition to signatures. Panic PIN wipes all the keys from the app. Software keys can be securely backed up. Full plausible deniability.
For example, a message can be transmitted by any means you prefer. Don't trust a popular messenger or email service? You can use this as an additional sturdy way of protecting it in advance. No metadata, no hidden flags. Just the encapsulated key + ciphertext with no marker of where one ends, and the other one - begins.
The app does not store any info about how you use it, what files or texts you encrypt. You can also encrypt stuff with your own key so you can store it anywhere without having to worry about someone else reading it (in that case signature is enforced so nobody else can make it look like it is a file you encrypted for yourself). File name is included in the ciphertext so it is preserved for once it is successfully decrypted.
I do have an android app prototype with full compatibility, but that is WIP due to android's different UI philosophy.
https://apps.apple.com/us/app/krypterapp/id6757750471
It does in many ways resemble good old GPG, but in a more lightweight form and without key directories.
Any feedback is appreciated so I can improve it and make an even better tool for everyone.