Embed Notice

Since it's all React.JS, I did the lazy thing: Looked in the assets directory for JavaScript files.

Success: assets/threads/Threads/encrypt.bundle and assets/threads/Threads/decrypt.bundle.

Unfortunately, this is just crypto-browserify and some other React libraries webpacked together.

It's full of side-channels and it's not clear which components are relevant.

Like, their ghash implementation (used by AES-GCM, which their decrypter uses) uses the && operation after comparing each bit of the state against 0, which short-circuits the right hand side. This introduces a timing side-channel that loudly exposes the entire GHASH state at any given point of time.

They also implemented AES with S-boxes in pure JavaScript (no bitslicing), which adds a cache-timing leak. Yay.

Their PKCS7 padding removal step for AES-CBC (which appears to be used for key-wrapping) also maximizes the timing leakage.

Suffice to say, the only cryptographic primitives I can find in their app are not recommended.