KRACK attacks hit Wi-Fi networks – the way out
The KRACK Attack is coming! The recent development – a Bug with a telling name
To be more precise, these are the KRACK Attacks, because there are several similar attacks that were introduced in the paper by KRACK.
So-called KRACK attacks are yet more proofs that many encrypted Wi-Fi networks are not as secure as you may think.
Using WPA and WPA2 encryption, KRACK affects many networks. It`s worth mentioning that nowadays the majority of wireless access points are covered exactly with this kind of encryption.
From the theoretical perspective, a criminal in your surrounding could spy out some of the encrypted traffic sent to one of the company computers.
A criminal can only fitfully transmit small amounts of traffic, but nevertheless, the consequences could be very dangerous.
Key Reinstallation Attack
KRACK stands for Key Reinstallation Attack and it`s unusual name that probably throws you for a loop when firstly heard about it, so this is the simplified explanation of what is going on.
At different times, an encrypted wireless connection requires you and the AP (access point) to reach an agreement about security keys.
For this procedure, both sides use so-called “four-way handshake” protocol, which contains the following information:
1.(AP to client) The agreement about a session key. Here`s some arbitrary data valid for one-time use in order to figure out it.
2.(Client to AP) WELL, here`s some arbitrary data from me, valid for one-time use.
At this stage, client and AP can combine the Wi-Fi network password (it`s so-called Pre-Shared Key or, in short, PSK) and two arbitrary blobs of data in order to create a one-time key for this particular session.
So, one doesn`t need to directly use the PSK in encrypting wireless data, and it guarantees a one-of-a-kind key for each session.
3.(AP to client) I`m affirming that we`ve agreed on enough data to create a key for this session.
4.(Client to AP) That`s true, we have.
The KRACK Attacks with different modifications exploit insecure implementation of this four-way protocol: most users didn`t follow appropriate instructions.
A criminal with a fake access point, which disguises as identical real network number can redirect message 4, so it wouldn`t reach the real AP.
During this pause, the client could start communicating with the AP, because they both can already use a session key in spite of the fact that the handshake wasn`t finished, actually.
Cryptographic material, known as the keystream, could already be distributed by the client with the view of encrypting the data it transfers.
In order to ensure a never-repeating keystream, the session key and “number used once” (in short: a nonce) are at the client`s disposal to encrypt each network frame. The nonce is incremented after each frame that leads to constant changes of the keystream.
Again about the handshake
At a certain point, another copy of message 3 will be sent by the genuine AP until the fake AP ultimately allows the message to reach the client.
The client completes formalities of the handshake and ‘reinstalls’ the session key (the attack`s name) in order to reset the keystream, and to startup the nonce to its state like after stage 2 of the handshake.
It means that the keystream begins to repeat itself and repeated usage of the keystream in a network encryption cipher of this kind is beyond the pale.
If the contents of the first-time encrypted network frames are known to you, you have opportunity to restore the keystream for their encryption. If you possess the keystream from the first spread of the network frames, you can decrypt the second-time encrypted frames.
But if one possesses even small amount of information, it`s already a real reason to worry.
The way out
The change of Wi-Fi password won`t resolve the problem, because this penetration doesn`t reset the password but provides a criminal with ability to decrypt the content of some sessions.
To change routers also won`t help, because Wi-Fi software implementations of the operating systems are the targets of many modifications of the KRACK Attacks.
Here are the steps to follow:
- Provide all Wi-Fi networks with open, unencrypted, wireless until further orders.
- Surf the HTTPS websites, so your web browsing is encrypted even if it uses an unencrypted connection.
- Make use of VPN, so all your network traffic will be encrypted, including your laptop or mobile phone, your home or work network.
- Use KRACK patches for your clients as fast as they are available.
In short, you immediately get into the world of inventive hackers and their tricks when using open or widely known Wi-Fi access points.
The conclusion is forced upon you: the safety measures you take on in these cases, must be implemented all the time.The KRACK Attack is coming! The recent development – a Bug with a telling name.