Description
We introduce key reinstallation attacks (KRACKs). These attacks abuse features of a protocol to reinstall an already in-use key, thereby resetting nonces and/or replay counters associated to this key. We show that our novel attack technique breaks several handshakes that are used in a WPA2-protected network.<br/> All protected Wi-Fi networks use the 4-way handshake to generate fresh session keys. The design of this handshake was proven secure, and over its 14-year lifetime no weaknesses have been found in it. However, contrary to this history, we show that the 4-way handshake is vulnerable to key reinstallation attacks. In such an attack, the adversary tricks a victim into reinstalling an already in-use key. This is achieved by manipulating and replaying handshake messages. When the victim reinstalls the key, the associated incremental nonce and replay counter is reset to its initial value. Apart from breaking the 4-way handshake, we also show that our key reinstallation attack breaks the group key and Fast BSS Transition (FT) handshake. The impact of our attacks depend on both the handshake being targeted, and the data-confidentiality protocol in use. Simplified, against AES-CCMP, an adversary can replay and decrypt packets, but cannot forge packets. Still, this makes it possible to hijack TCP streams and inject malicious data into them. Against WPA-TKIP and GCMP, the impact is catastrophic: an adversary can replay, decrypt, and forge arbitrary packets. Rather surprisingly, GCMP is especially affected because it uses the same authentication key in both communication directions. Finally, we confirmed our findings in practice, and found that every Wi-Fi device is vulnerable to some variant of our attacks. Notably, our attack is exceptionally devastating against Android and Linux: it forces the client into using a predictable all-zero encryption key.
Next sessions
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On the average hardness of SIVP for module lattices of fixed rank
Speaker : Radu Toma - Sorbonne Université
In joint work with Koen de Boer, Aurel Page, and Benjamin Wesolowski, we study the hardness of the approximate Shortest Independent Vectors Problem (SIVP) for random module lattices. We use here a natural notion of randomness as defined originally by Siegel through Haar measures. By proving a reduction, we show it is essentially as hard as the problem for arbitrary instances. While this was[…] -
Attacks and Remedies for Randomness in AI: Cryptanalysis of PHILOX and THREEFRY
Speaker : Yevhen Perehuda - Ruhr-University Bochum
In this work, we address the critical yet understudied question of the security of the most widely deployed pseudorandom number generators (PRNGs) in AI applications. We show that these generators are vulnerable to practical and low-cost attacks. With this in mind, we conduct an extensive survey of randomness usage in current applications to understand the efficiency requirements imposed in[…]-
Cryptography
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Lightweight (AND, XOR) Implementations of Large-Degree S-boxes
Speaker : Marie Bolzer - LORIA
The problem of finding a minimal circuit to implement a given function is one of the oldest in electronics. In cryptography, the focus is on small functions, especially on S-boxes which are classically the only non-linear functions in iterated block ciphers. In this work, we propose new ad-hoc automatic tools to look for lightweight implementations of non-linear functions on up to 5 variables for[…]-
Cryptography
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Symmetrical primitive
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Implementation of cryptographic algorithm
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Algorithms for post-quantum commutative group actions
Speaker : Marc Houben - Inria Bordeaux
At the historical foundation of isogeny-based cryptography lies a scheme known as CRS; a key exchange protocol based on class group actions on elliptic curves. Along with more efficient variants, such as CSIDH, this framework has emerged as a powerful building block for the construction of advanced post-quantum cryptographic primitives. Unfortunately, all protocols in this line of work are[…] -
Endomorphisms via Splittings
Speaker : Min-Yi Shen - No Affiliation
One of the fundamental hardness assumptions underlying isogeny-based cryptography is the problem of finding a non-trivial endomorphism of a given supersingular elliptic curve. In this talk, we show that the problem is related to the problem of finding a splitting of a principally polarised superspecial abelian surface. In particular, we provide formal security reductions and a proof-of-concept[…]-
Cryptography
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