On Length Independent Security Bounds for the PMAC Family

At FSE 2017, Gaži et al. demonstrated a pseudorandom function (PRF) distinguisher (Gaži et al., ToSC 2016(2)) on PMAC with Ω(lq2/2n) advantage, where q, l, and n, denote the number of queries, maximum permissible query length (in terms of n-bit blocks), and block size of the underlying block cipher. This, in combination with the upper bounds of Ο(lq2/2n) (Minematsu and Matsushima, FSE 2007) and Ο(qσ/2n) (Nandi and Mandal, J. Mathematical Cryptology 2008(2)), resolved the long-standing problem of exact security of PMAC. Gaži et al. also showed that the dependency on l can be dropped (i.e. O(q2/2n) bound up to l ≤ 2n/2) for a simplified version of PMAC, called sPMAC, by replacing the Gray code-based masking in PMAC with any 4-wise independent universal hash-based masking. Recently, Naito proposed another variant of PMAC with two powering-up maskings (Naito, ToSC 2019(2)) that achieves l-free bound of O(q2/2n), provided l ≤ 2n/2. In this work, we first identify a flaw in the analysis of Naito’s PMAC variant that invalidates the security proof. Apparently, the flaw is not easy to fix under the existing proof setup. We then formulate an equivalent problem which must be solved in order to achieve l-free security bounds for this variant. Second, we show that sPMAC achieves O(q2/2n) bound for a weaker notion of universality as compared to the earlier condition of 4-wise independence. Third, we analyze the security of PMAC1 (a popular variant of PMAC) with a simple modification in the linear combination of block cipher outputs. We show that this simple modification of PMAC1 has tight security O(q2/2n) provided l ≤ 2n/4. Even if l < 2n/4, we still achieve same tight bound as long as total number of blocks in all queries is less than 22n/3.

Feature Reduction in MANET using Machine Learning Language

Mobile ad-hoc network (MANET) is an infrastructure-less network. Therefore, MANET involves a selection of exact security schemes to notice the false entrance of the mischievous nodes. Along these lines, we require solid instrument to identify these pernicious nodes and to arrange ordinary and irregular nodes based on the conduct or performance of nodes. Machine learning system nowadays used to built a best IDS for recognizing exception or misbehaving nodes rapidly and precisely give grouping by watching conduct of those nodes in the system. In MANET system, numbers of parameters are taken for analysation. It makes the IDS system complex. To avoid this complexity many techniques are derived for feature reduction. In this proposed work, we are testing how feature reduction can be done using Python machine learning program.

Data Extraction in Malignant Environments

Deliberate or inadvertent escape of classified data is undoubtedly one among the premier extreme security dangers that associations look inside the advanced period. The risk right now stretches out to the private lives: an abundance of private information is out there to interpersonal organizations and great telephone providers and is in a roundabout way exchanged to undependable outsider and fourth gathering applications. amid this work, a bland data genealogy structure LIME (Data Lineage in the Malicious Environment), is utilized for data stream over different elements that take two trademark, guideline parts (i.e., proprietor and buyer). It characterizes the exact security ensures required by such a data heredity component toward recognizable proof of a blameworthy substance, and decide the disentangling non-denial and trustworthiness suspicions. At that point create and break down a totally special dependable data exchange convention between two substances among noxious surroundings by expanding upon unmindful exchange, solid watermarking, and mark natives. At long last, an exploratory investigation to exhibit the helpfulness of convention what's more, apply structure to the important data run projections of learning outsourcing and the informal organizations. In general, LIME(Data Lineage in the Malicious Environment),lineage structure for information exchange, to be a key advance towards accomplishing responsibility by plan.

Security Measurement for Unknown Threats Based on Attack Preferences

Security measurement matters to every stakeholder in network security. It provides security practitioners the exact security awareness. However, most of the works are not applicable to the unknown threat. What is more, existing efforts on security metric mainly focus on the ease of certain attack from a theoretical point of view, ignoring the “likelihood of exploitation.” To help administrator have a better understanding, we analyze the behavior of attackers who exploit the zero-day vulnerabilities and predict their attack timing. Based on the prediction, we propose a method of security measurement. In detail, we compute the optimal attack timing from the perspective of attacker, using a long-term game to estimate the risk of being found and then choose the optimal timing based on the risk and profit. We design a learning strategy to model the information sharing mechanism among multiattackers and use spatial structure to model the long-term process. After calculating the Nash equilibrium for each subgame, we consider the likelihood of being attacked for each node as the security metric result. The experiment results show the efficiency of our approach.

Tight Security Analysis of EHtM MAC

The security of a probabilistic Message Authentication Code (MAC) usually depends on the uniqueness of the random salt which restricts the security to birthday bound of the salt size due to the collision on random salts (e.g XMACR). To overcome the birthday bound limit, the natural approach to use (a) either a larger random salt (e.g MACRX3 uses 3n bits of random salt where n is the input and output size of the underlying non-compressing pseudorandom function or PRF) or (b) a PRF with increased domain size (e.g RWMAC or Randomized WMAC). Enhanced Hashthen- Mask (EHtM), proposed by Minematsu in FSE 2010, is the first probabilistic MAC scheme that provides beyond birthday bound security without increasing the randomness of the salt and the domain size of the non-compressing PRF. The author proved the security of EHtM as long as the number of MAC query is smaller than 22n/3 where n is the input size of the underlying non-compressing PRF. In this paper, we provide the exact security bound of EHtM and prove that this construction offers security up to 23n/4 MAC queries. The exactness is shown by demonstrating a matching attack.

On The Exact Security of Message Authentication Using Pseudorandom Functions

Traditionally, modes of Message Authentication Codes(MAC) such as Cipher Block Chaining (CBC) are instantiated using block ciphers or keyed Pseudo Random Permutations(PRP). However, one can also use domain preserving keyed Pseudo Random Functions(PRF) to instantiate MAC modes. The very first security proof of CBC-MAC [BKR00], essentially modeled the PRP as a PRF. Until now very little work has been done to investigate the difference between PRP vs PRF instantiations. Only known result is the rather loose folklore PRP-PRF transition of any PRP based security proof, which looses a factor of Ο( σ2/2n ) (domain of PRF/PRP is {0, 1}n and adversary makes σ many PRP/PRF calls in total). This loss is significant, considering the fact tight Θ( q2/2n ) security bounds have been known for PRP based EMAC and ECBC constructions (where q is the total number of adversary queries). In this work, we show for many variations of encrypted CBC MACs (i.e. EMAC, ECBC, FCBC, XCBC and TCBC), random function based instantiation has a security bound Ο( qσ/2n ). This is a significant improvement over the folklore PRP/PRF transition. We also show this bound is optimal by providing an attack against the underlying PRF based CBC construction. This shows for EMAC, ECBC and FCBC, PRP instantiations are substantially more secure than PRF instantiations. Where as, for XCBC and TMAC, PRP instantiations are at least as secure as PRF instantiations.

The Exact Security of PMAC

PMAC is a simple and parallel block-cipher mode of operation, which was introduced by Black and Rogaway at Eurocrypt 2002. If instantiated with a (pseudo)random permutation over n-bit strings, PMAC constitutes a provably secure variable input-length (pseudo)random function. For adversaries making q queries, each of length at most l (in n-bit blocks), and of total length σ ≤ ql, the original paper proves an upper bound on the distinguishing advantage of Ο(σ2/2n), while the currently best bound is Ο (qσ/2n).In this work we show that this bound is tight by giving an attack with advantage Ω (q2l/2n). In the PMAC construction one initially XORs a mask to every message block, where the mask for the ith block is computed as τi := γi·L, where L is a (secret) random value, and γi is the i-th codeword of the Gray code. Our attack applies more generally to any sequence of γi’s which contains a large coset of a subgroup of GF(2n). We then investigate if the security of PMAC can be further improved by using τi’s that are k-wise independent, for k > 1 (the original distribution is only 1-wise independent). We observe that the security of PMAC will not increase in general, even if the masks are chosen from a 2-wise independent distribution, and then prove that the security increases to O(q<2/2n), if the τi are 4-wise independent. Due to simple extension attacks, this is the best bound one can hope for, using any distribution on the masks. Whether 3-wise independence is already sufficient to get this level of security is left as an open problem.