An introduction to mobile messaging and analysis of the Threema protocol [video]

They are taking apart Threema. While it's not open-source, it's not exactly a "black box" either -

https://threema.ch/press-files/cryptography_whitepaper.pdf

Ok, we replaced 'black box' with 'Threema' above.

How about using the official subtitle 'A gentle introduction to mobile messaging and subsequent analysis of the Threema protocol.'?

Ok, we can shorten that to fit.

Excellent, nice work. Have been a fan of Threema for a long time.

Would be so great if they open sourced it.

I doubt that it'll going to happen soon: https://threema.ch/en/faq/source_code

On the other hand, the web client they're about to release _is_ open source.

Anyway, it's the most secure messenger at the moment, IMHO, and I love the fact that no phone number is required.

I think it's the best messenger I have used all around, in terms of UI.

I particularly like their take on the verification levels using a traffic light metaphor - giving visual feedback on how well trusted a contact is on my list; I wish other clients would adopt it something similar and encourage more people to verify keys out of band.

Agreed, the UI is very clean and polished. (I use the Android version.)