WhatsApp New Vulnerability

The popular Android mobile messaging application WhatsApp Messenger has a major design flaw in its cryptographic implementation that could allow attackers to decrypt intercepted messages, It has been announced by a Dutch developer.

Actually the problem comes with that the same key is used to encrypt both outgoing and incoming streams between the client and the WhatsApp server, said Thijs Alkemade, a computer science and mathematics student at Utrecht University in the Netherlands and lead developer of the open-source Adium instant messaging client for Mac OS X.

Mr.Alkemade Said thesday on his blog regarding this 

“RC4 is a PRNG [pseudo-random number generator] that generates a stream of bytes, which are xored [a crypto operation] with the plaintext that is to be encrypted. By xoring the ciphertext with the same stream, the plaintext is recovered,” 

They said one more too, if two messages are encrypted with the same key and an attacker can intercept them, like on an open wireless network, he can analyze them to cancel out the key and eventually recover the original plaintext information.

Reusing the key in this manner is a basic crypto implementation error that the WhatsApp developers should have been aware of, Alkemade said Wednesday. It’s a mistake made by the Soviets in the 1950s and by Microsoft in its VPN software in 1995.

Alkemade had released the screenshot of exploit code for the WhatsApp vulnerabilty, but initially tested it on the WhatsPoke open-source library, not on the official WhatsApp client.Since then he has confirmed that the issue exists in the WhatsApp clients for Nokia Series 40 and Android devices.

Actually the mistakes are same encryption key in both directions, and also same HMAC key in both directions.

Alkemade confirmed that there is no remediation for the flaw in this moment, that's why he suggest to stop using WhatsApp until developers produce a patch.