One problem with closed source end-to-end encryption is the trust you have to put into the vendor. The encryption implementation may be excellent, but what's to

One problem with closed source end-to-end encryption is the trust you have to put into the vendor. The encryption implementation may be excellent, but what's to stop them from adding a "upload private key" function for lawful interception, perhaps at a later time? It's the same issue with WhatsApp. I hear rumors that law enforcement can access WhatsApp messages so i guess there must be a backdoor like this.