A Novel WLAN Client Puzzle against DoS Attack Based on Pattern Matching

Despite the popularity of 802.11 based networks, they suffer several types of DoS attack, launched by an attacker whose aim is to make an access point (AP) unavailable to legitimate users. One of the most common DoS attacks on 802.11 based networks is to deplete the resources of the AP. A serious situation like this can occur when the AP receives a burst of connection requests. This paper addresses this common DoS attack and proposes a lightweight puzzle, based on pattern-matching. Using a pattern-matching technique, this model adequately resists resource-depletion attacks in terms of both puzzle generation and solution verification. Using a sensible series of contextual comparisons, the outcomes were modelled by a simulator, and the security definition and proofs are verified, among other results

Spinorial geometry and Killing spinor equations of 6-D supergravity

We solve the Killing spinor equations of 6-dimensional (1,0)-supergravity coupled to any number of tensor, vector and scalar multiplets in all cases. The isotropy groups of Killing spinors are Sp(1)\cdot Sp(1)\ltimes \bH (1), U(1)\cdot Sp(1)\ltimes \bH (2), Sp(1)\ltimes \bH (3,4), $Sp(1) (2)$, $U(1) (4)$ and $\{1\} (8)$, where in parenthesis is the number of supersymmetries preserved in each case. If the isotropy group is non-compact, the spacetime admits a parallel null 1-form with respect to a connection with torsion the 3-form field strength of the gravitational multiplet. The associated vector field is Killing and the 3-form is determined in terms of the geometry of spacetime. The Sp(1)\ltimes \bH case admits a descendant solution preserving 3 out of 4 supersymmetries due to the hyperini Killing spinor equation. If the isotropy group is compact, the spacetime admits a natural frame constructed from 1-form spinor bi-linears. In the $Sp(1)$ and U(1) cases, the spacetime admits 3 and 4 parallel 1-forms with respect to the connection with torsion, respectively. The associated vector fields are Killing and under some additional restrictions the spacetime is a principal bundle with fibre a Lorentzian Lie group. The conditions imposed by the Killing spinor equations on all other fields are also determined.Comment: 34 pages, Minor change

IST Austria Thesis

In this thesis we discuss the exact security of message authentications codes HMAC , NMAC , and PMAC . NMAC is a mode of operation which turns a fixed input-length keyed hash function f into a variable input-length function. A practical single-key variant of NMAC called HMAC is a very popular and widely deployed message authentication code (MAC). PMAC is a block-cipher based mode of operation, which also happens to be the most famous fully parallel MAC. NMAC was introduced by Bellare, Canetti and Krawczyk Crypto’96, who proved it to be a secure pseudorandom function (PRF), and thus also a MAC, under two assumptions. Unfortunately, for many instantiations of HMAC one of them has been found to be wrong. To restore the provable guarantees for NMAC , Bellare [Crypto’06] showed its security without this assumption. PMAC was introduced by Black and Rogaway at Eurocrypt 2002. If instantiated with a pseudorandom permutation over n -bit strings, PMAC constitutes a provably secure variable input-length PRF. For adversaries making q queries, each of length at most ` (in n -bit blocks), and of total length σ ≤ q` , the original paper proves an upper bound on the distinguishing advantage of O ( σ 2 / 2 n ), while the currently best bound is O ( qσ/ 2 n ). In this work we show that this bound is tight by giving an attack with advantage Ω( q 2 `/ 2 n ). In the PMAC construction one initially XORs a mask to every message block, where the mask for the i th block is computed as τ i := γ i · L , where L is a (secret) random value, and γ i is the i -th codeword of the Gray code. Our attack applies more generally to any sequence of γ i ’s which contains a large coset of a subgroup of GF (2 n ). As for NMAC , our first contribution is a simpler and uniform proof: If f is an ε -secure PRF (against q queries) and a δ - non-adaptively secure PRF (against q queries), then NMAC f is an ( ε + `qδ )-secure PRF against q queries of length at most ` blocks each. We also show that this ε + `qδ bound is basically tight by constructing an f for which an attack with advantage `qδ exists. Moreover, we analyze the PRF-security of a modification of NMAC called NI by An and Bellare that avoids the constant rekeying on multi-block messages in NMAC and allows for an information-theoretic analysis. We carry out such an analysis, obtaining a tight `q 2 / 2 c bound for this step, improving over the trivial bound of ` 2 q 2 / 2 c . Finally, we investigate, if the security of PMAC can be further improved by using τ i ’s that are k -wise independent, for k > 1 (the original has k = 1). We observe that the security of PMAC will not increase in general if k = 2, and then prove that the security increases to O ( q 2 / 2 n ), if the k = 4. Due to simple extension attacks, this is the best bound one can hope for, using any distribution on the masks. Whether k = 3 is already sufficient to get this level of security is left as an open problem. Keywords: Message authentication codes, Pseudorandom functions, HMAC, PMAC

Revisiting Full-PRF-Secure PMAC and Using It for Beyond-Birthday Authenticated Encryption

This paper proposes an authenticated encryption scheme, called SIVx, that preserves BBB security also in the case of unlimited nonce reuses. For this purpose, we propose a single-key BBB-secure message authentication code with 2n-bit outputs, called PMAC2x, based on a tweakable block cipher. PMAC2x is motivated by PMAC_TBC1k by Naito; we revisit its security proof and point out an invalid assumption. As a remedy, we provide an alternative proof for our construction, and derive a corrected bound for PMAC_TBC1k

QCB is Blindly Unforgeable

QCB is a proposal for a post-quantum secure, rate-one authenticated encryption with associated data scheme (AEAD) based on classical OCB3 and $\Theta$CB, which are vulnerable against a quantum adversary in the Q2 setting. The authors of QCB prove integrity under plus-one unforgeability, whereas the proof of the stronger definition of blind unforgeability has been left as an open problem. After a short overview of QCB and the current state of security definitions for authentication, this work proves blind unforgeability of QCB. Finally, the strategy of using tweakable block ciphers in authenticated encryption is generalised to a generic blindly unforgeable AEAD model

Re-engineering jake2 to work on a grid using the GridGain Middleware

With the advent of Massively Multiplayer Online Games (MMOGs), engineers and designers of games came across with many questions that needed to be answered such as, for example, "how to allow a large amount of clients to play simultaneously on the same server?", "how to guarantee a good quality of service (QoS) to a great number of clients?", "how many resources will be necessary?", "how to optimize these resources to the maximum?". A possible answer to these questions relies on the usage of grid computing. Taking into account the parallel and distributed nature of grid computing, we can say that grid computing allows for more scalability in terms of a growing number of players, guarantees shorter communication time between clients and servers, and allows for a better resource management and usage (e.g., memory, CPU, core balancing usage, etc.) than the traditional serial computing model. However, the main focus of this thesis is not about grid computing. Instead, this thesis describes the re-engineering process of an existing multiplayer computer game, called Jake2, by transforming it into a MMOG, which is then put to run on a grid

DNA-based client puzzle for WLAN association protocol against connection request flooding

In recent past, Wireless Local Area Network (WLAN) has become more popular because of its flexibility. However, WLANs are subjected to different types of vulnerabilities. To strengthen WLAN security, many high security protocols have been developed. But those solutions are found to be ineffective in preventing Denial of Service (DoS) attacks. A ‘Connection Request Flooding’ DoS (CRF-DoS) attack is launched when an access point (AP) encounters a sudden explosion of connection requests. Among other existing anti CRF-DoS methods, a client puzzle protocol has been noted as a promising and secure potential solution. Nonetheless, so far none of the proposed puzzles satisfy the security requirement of resource-limited and highly heterogeneous WLANs. The CPU disparity, imposing unbearable loads on legitimate users, inefficient puzzle generation and verification algorithms; the susceptibility of puzzle to secondary attacks on legitimate users by embedding fake puzzle parameters; and a notable delay in modifying the puzzle difficulty – these are some drawbacks of currently existing puzzles. To deal with such problems, a secure model of puzzle based on DNA and queuing theory is proposed, which eliminates the above defects while satisfying the Chen puzzle security model. The proposed puzzle (OROD puzzle) is a multifaceted technology that incorporates five main components include DoS detector, queue manager, puzzle generation, puzzle verification, and puzzle solver. To test and evaluate the security and performance, OROD puzzle is developed and implemented in real-world environment. The experimental results showed that the solution verification time of OROD puzzle is up to 289, 160, 9, 3.2, and 2.3 times faster than the Karame-Capkun puzzle, the Rivest time-lock puzzle, the Rangasamy puzzle, the Kuppusamy DLPuz puzzle, and Chen's efficient hash-based puzzle respectively. The results also showed a substantial reduction in puzzle generation time, making the OROD puzzle from 3.7 to 24 times faster than the above puzzles. Moreover, by asking to solve an easy and cost-effective puzzle in OROD puzzle, legitimate users do not suffer from resource exhaustion during puzzle solving, even when under severe DoS attack (high puzzle difficulty)