[rocqua]

> This is not a backdoor, this is a default setting of > WhatsApp and everybody is able to opt-in the feature > which blocks message sending when the key material changes.

This is flat-out wrong. There is no opt-in feature to block sending when the key material changes. There is only an option that notifies when the material changes.

And this is precisely the problem. On certain messages (those not yet delivered) whatsapp can force re-transmission encrypted with a key of their choosing. No options will block the re-transmission.