WhatsApp uses a customised version of XMPP (Extensible Messaging and Presence Protocol) as the communication protocol. Upon installation, it creates a user account using one’s phone number (with country code prefix) as the username (Jabber ID:
[phone number]@s.whatsapp.net). A password is generated using an unknown algorithm on the server end and sent to the client. Previously the password was derived from the phone’s IMEI or the WiFi MAC address.
A couple of weeks back, WhatsApp introduced a new way of encrypting the backup messages saved on the SD card. The article that I wrote last month on decrypting the WhatsApp messages will no longer work on the new