As reported previously by various media outlets, the bug, dubbed “KRACK” — which stands for Key Reinstallation Attack — is at heart a fundamental flaw in the way Wi-Fi Protected Access II (WPA2) operates. The Krack attack was discovered by researchers Mathy Vanhoef and Frank Piessens of KU Leuven in Belgium was revealed on Monday, 10-16-2017.
The security protocol, an upgrade from WPA, is used to protect and secure communications between everything from routers, mobile devices, and Internet of Things (IoT) devices, but there is an issue in the system’s four-way handshake which permits devices with a pre-shared password to join a network.
The 4-way handshake is executed when a client wants to join a protected Wi-Fi network, and is used to confirm that both the client and access point possess the correct credentials (e.g. the pre-shared password of the network). At the same time, the 4-way handshake also negotiates a fresh encryption key that will be used to encrypt all subsequent traffic. Currently, all modern protected Wi-Fi networks use the 4-way handshake. This implies all these networks are affected by (some variant of) this attack. For instance, the attack works against personal and enterprise Wi-Fi networks, against the older WPA and the latest WPA2 standard, and even against networks that only use AES.
In a key reinstallation attack, KRACK, the adversary tricks a victim into reinstalling an already-in-use key. This is achieved by manipulating and replaying cryptographic handshake messages. When the victim reinstalls the key, associated parameters such as the incremental transmit packet number (i.e. nonce) and receive packet number (i.e. replay counter) are reset to their initial value, thus allowing to abuse this weakness in practice.
The research continues to state that since the initial publication, researchers have now uncovered that the TDLS handshake and WNM Sleep Mode Response frame are also vulnerable to key reinstallation attacks.
While Windows and iOS devices are not vulnerable to the four-way handshake attack, they are vulnerable to the group key handshake attack.
Android 6.0, Chromium and Android Wear 2.0 devices are particularly vulnerable to four-way handshake attacks – an attack actually causes the protocol to reinstall a predictable, all-zero key, making it trivial to decrypt the network’s traffic.
Decryption of packets will result in interception of sensitive information such as passwords, cookies, and other types of PII data.
To prevent the attack, users must update affected products as soon as security updates become available.
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