Cryptocat is an encrypted chatting service that lets no one apart from the sender and receiver see the actual content of the message. The developer of the service recently submitted an iPhone Cryptocat app, but it was rejected by Apple for “illegitimate” reasons.

Nadim Kobeissi, the developer of the app, said:

Cryptocat for iPhone was just rejected from the Apple app store. NDA doesn’t allow me to discuss openly but reasons are truly illegitimate.

One of the reasons for Cryptocat for iPhone’s rejection by Apple strongly implies that any other encrypted group chat app can be rejected.

In followup tweets, Kobeissi says that Apple specifically had a problem with group chat encryption, and that he’s working with the Electronic Frontier Foundation (EFF) to discuss the rejection. What’s strange is that Apple has already approved the Cryptocat Mac app on the Mac App Store, which requires developers to comply to similar rules.

Cryptocat became popular in wake of the NSA controversy, where the agency was found to intercept and snoop on communications. Cryptocat’s end-to-end encryption by design doesn’t allow for anyone in the middle to read your messages.

If you’re interested in learning more, you can head over to Cryptocat’s website, or check out the source code of the unreleased iPhone app.