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.
Prochains exposés
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Combining Partial Sums and FFT for the Fastest Known Attack on 6‑Round AES
Orateur : Shibam Ghosh - Inria
The partial-sums technique introduced by Ferguson et al. (2000) achieved a 6‑round AES attack with time complexity 2^{52} S‑box evaluations, a benchmark that has stood since. In 2014, Todo and Aoki proposed a comparable approach based on the Fast Fourier Transform (FFT). In this talk, I will show how to combine partial sums with FFT to get "the best of both worlds". The resulting attack on 6[…]-
Cryptography
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Lie algebras and the security of cryptosystems based on classical varieties in disguise
Orateur : Mingjie Chen - KU Leuven
In 2006, de Graaf et al. proposed a strategy based on Lie algebras for finding a linear transformation in the projective linear group that connects two linearly equivalent projective varieties defined over the rational numbers. Their method succeeds for several families of “classical” varieties, such as Veronese varieties, which are known to have large automorphism groups. In this talk, we[…]-
Cryptography
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Some applications of linear programming to Dilithium
Orateur : Paco AZEVEDO OLIVEIRA - Thales & UVSQ
Dilithium is a signature algorithm, considered post-quantum, and recently standardized under the name ML-DSA by NIST. Due to its security and performance, it is recommended in most use cases. During this presentation, I will outline the main ideas behind two studies, conducted in collaboration with Andersson Calle-Vierra, Benoît Cogliati, and Louis Goubin, which provide a better understanding of[…] -
Wagner’s Algorithm Provably Runs in Subexponential Time for SIS^∞
Orateur : Johanna Loyer - Inria Saclay
At CRYPTO 2015, Kirchner and Fouque claimed that a carefully tuned variant of the Blum-Kalai-Wasserman (BKW) algorithm (JACM 2003) should solve the Learning with Errors problem (LWE) in slightly subexponential time for modulus q = poly(n) and narrow error distribution, when given enough LWE samples. Taking a modular view, one may regard BKW as a combination of Wagner’s algorithm (CRYPTO 2002), run[…]-
Cryptography
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CryptoVerif: a computationally-sound security protocol verifier
Orateur : Bruno Blanchet - Inria
CryptoVerif is a security protocol verifier sound in the computational model of cryptography. It produces proofs by sequences of games, like those done manually by cryptographers. It has an automatic proof strategy and can also be guided by the user. It provides a generic method for specifying security assumptions on many cryptographic primitives, and can prove secrecy, authentication, and[…]-
Cryptography
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Structured-Seed Local Pseudorandom Generators and their Applications
Orateur : Nikolas Melissaris - IRIF
We introduce structured‑seed local pseudorandom generators (SSL-PRGs), pseudorandom generators whose seed is drawn from an efficiently sampleable, structured distribution rather than uniformly. This seemingly modest relaxation turns out to capture many known applications of local PRGs, yet it can be realized from a broader family of hardness assumptions. Our main technical contribution is a[…]-
Cryptography
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