Microsoft wireless keyboards crypto cracked

Tapping up



Bluetooth is increasingly becoming the de-facto standard for wireless communication in peripheral devices and is reckoned to be secure. But some manufacturers such as Logitech and Microsoft rely on 27 MHz radio technology which, it transpires, is anything but secure.

Using nothing more than a simple radio receiver, a soundcard and suitable software, Swiss security firm Dreamlab Technologies managed to capture and decode the radio communications between a keyboard and a PC. The attack opens the way up to all sorts of mischief including keystroke logging to capture login credentials to online banking sites or email accounts.

Dreamlab cracked the encryption key used within Microsoft Wireless Optical Desktop 1000 and 2000 keyboards. As most products in Microsoft's wireless range are based on the same technology other products are likely to be insecure. Max Moser and Phillipp Schrödel of Dreamlab Technologies succeeded in eavesdropping traffic from a distance of up to ten meters using a simple radio receiver. More sensitive receivers may make it possible to capture keystrokes over larger distances.

Sniffing traffic between wireless keyboards and their base stations was possible because of the weak encryption used, as explained in a white paper from Dreamlab:

To our surprise, only the actual keystroke data seems to be encrypted. The Metaflags and identifier bits aren't encrypted or obfuscated. The one byte USB Hid code is encrypted using a simple XOR mechanism with a single byte of random data generated during the association procedure.

This means that there are only 256 different key values possible per keyboard and receiver pair. We did not notice any automated key change interval and therefore assume that the encryption key stays the same until the user reassociates the keyboard. 256 key combination can be brute forced even with very slow computers today. We did not analyze the quality of the random number so far because it was not needed to successfully break the encryption.

"Wireless communication is only as secure as the encryption technology used. Due to its nature, it can be tapped with little effort," said Dreamlab's Max Moser.

Dreamlab has reported the security loophole to Microsoft. The security researchers are holding off releasing details on exactly how the hack was pulled off pending the release of a fix, which it reckons may be a difficult and drawn-out process. The security researchers have however published a video of the attack here. ®

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