# Tag Info

8

As Thomas pointed out in his comment, in WPA-PSK the parties already have a shared secret (the pre-shared key), so there is no need to go through the step of Diffie-Hellman key-exchange -- unless you want perfect forward secrecy (PFS) (see update below). In WPA, the client and the access point goes through a step known as the "4-way-handshake" to verify ...

8

Well, it depends on the which protocol is being used. For WEP and WPA, the keys used are derived directly from the pre-shared keys; that means that as long as you know the pre-shared keys, you can immediately decrypt packets as well. On the other hand, WPA2 is somewhat stronger; the two sides exchange nonces to derive the keys. Hence, unless you listen ...

8

Curiously, the answer is »Yes« to both questions. Each client (STA) establishes a different pairwise transient key (PTK) with the access point (AP) for each session, but this PTK is derived from the pairwise master key (PMK). And if you are using a pre-shared key (PSK, usually derived from a password entered by the users), this PSK is used as the PMK. The ...

6

A key is derived from the password using a Password Based Key Derivation Function, in this case PBKDF2: Key = PBKDF2(HMAC−SHA1, passphrase, ssid, 4096, 256) PBKDF2 in turn is described by PKCS#5. These RSA cryptographic standards in turn are made available through RFC's nowadays, in this case RFC 2898: PKCS #5: Password-Based Cryptography Specification ...

5

This approach is likely not novel, but just an application of covert channel. This is example of paper about detecting UDP packet length steganography. Because there has been already packet length used for messaging so often that even its detection has been discussed in papers, this cannot be very novel. However, often the use of such side-channel is used ...

3

Part of the problem you're having is that there are multiple distinct vulnerabilities in WEP, and you're getting confused by the sheer number. For example: I still don't have an understanding of how one might exploit [repeating IVs] to retrieve the key Answer: those are two separate vulnerabilities. The shortness of the IV space is an obvious ...

3

Yes. Both WPA-TKIP and WPA2-AES use the same 4-way handshake, and the same way of deriving the PTK from the PSK. AES does not affect this. To launch the brute-force attack on the PSK you only need to capture the 4-way handshake (including the nonces). This is also true for WPA2-AES-PSK.

2

Using DH with public keys signed by the network wide PSK does not prevent station performing MITM attacks on each other. Further, if the PSK is weak a brute force attack on the signature applied to the public key can be a viable off line strategy. Subsequently to determining the PSK, the unauthorised 3rd party could then use the MITM attack to decrypt ...

2

It's the same reason why open WIFI isn't encrypted. It is feasible and we have the technology and means, but the problem lies in our inefficient nature as humans. It makes perfect sense to use Diffie-Hellman/RSA, yet someone up there decided to standardize it in a non optimal way. The world is inefficient and standards move slower than mountains, numerous ...

1

The following answers are taken directly from the 802.11 standard (2012 version). The PTK is generated as follows: $$\mathrm{PTK} \gets \operatorname{\mathrm{PRF-X}(PMK, pairwise \ key \ expansion", \\ min(AA, SPA) || max(AA,SPA)|| \\ min(ANonce, SNonce) || max(ANonce, SNonce)) }$$ where $\mathrm{AA}$ and $\mathrm{SPA}$ are the MAC addresses of the ...

1

In pairwise key hierarchy there are two root keys: pre-shared key (PSK) and Authentication, Authorization, and Accounting Key (AAAK). From these two keys pairwise master key (PMK) is derived. In the case of PSK, PMK is equal to PSK. In other case, PMK is obtained by taking the first 256 bits of AAAK. Now, to the question about generating pairwise transient ...

1

No, two messages is not sufficient to achieve what the WPA2-PSK 4WHS is supposed to do: mutual authenticated key-exchange. The key term here is mutual authentication. Remember, at the start of the WPA2-PSK handshake we have two entities, the access point and the client, holding (hopefully) the same key, also known as the pairwise master key (PMK). Now they ...

1

Specifically to answer your question of whether or no using the packet size in a wireless network is novel, the answer is no. See http://www.cs.washington.edu/research/projects/poirot3/Oakland/sp/PAPERS/2008/3168A311.PDF Specifically in Section 4: The exploit field chosen for the experiment is the 16- bit packet size field of a link layer protocol ...

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