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Typical protocols for password-based authentication assume a single server which stores all the information (e.g.), the password necessary to authenticate a user. Unfortunately, an inherent limitation of this approach (assuming low-entropy passwords are used) is that the user’s password is exposed if this server is ever compromised. To address this issue, a number of schemes have been proposed in...
Passwords are one of the most common cause of system break-ins, because the low entropy of passwords makes systems vulnerable to brute force guessing attacks (dictionary attacks). Existing Strong Password-based Authentication and Key Agreement (SPAKA) protocols protect passwords from passive (eavesdropping-offline dictionary) attacks, but not from active online dictionary attacks. This paper presents...
Password-Authenticated Key Establishment (PAKE) protocols allow two parties, to share common secret keys in an authentic manner based on an easily memorizable password. At ICCSA 2004, an improved PAKE protocol between two clients of different realms was proposed that was claimed to be secure against attacks including the replay attack. In this paper, we cryptanalyze this protocol by showing two replay...
This paper studies the security issues that arise in an overlay multicast architecture where service providers distribute content such as web pages, static and streaming multimedia data, realtime stock quotes, or security updates to a large number of users. In particular, two major security problems of overlay multicast, network access control and group key management, are addressed. We first present...
We describe a fully k-resilient traitor tracing scheme that utilizes RSA as a secret-key rather than public-key cryptosystem. Traitor tracing schemes deter piracy in broadcast encryption systems by enabling the identification of authorized users known as traitors that contribute to unauthorized pirate decoders. In the proposed scheme, upon the confiscation of a pirate decoder created by a collusion...
We consider the problem of password-authenticated group Diffie-Hellman key exchange among N parties, N–1 clients and a single-server, using different passwords. Most password-authenticated key exchange schemes in the literature have focused on an authenticated key exchange using a shared password between a client and a server. With a rapid change in modern communication environment such as ad-hoc...
We have developed techniques to automatically infer mother’s maiden names from public records. We demonstrate our techniques using publicly available records from the state of Texas, and reduce the entropy of a mother’s maiden name from an average of close to 13 bits down to below 6.9 bits for more than a quarter of the people targeted, and down to a zero entropy (i.e., certainty of their mothers...
In this paper we explore the feasibility of mitigating network denial-of-service (NDoS) attacks (attacks that consume network bandwidth) by dynamically regulating learned classes of network traffic. Our classification technique clusters packets based on the similarity of their contents – both headers and payloads – using a variation of n-grams which we call (p,n)-grams. We then allocate shares of...
High-value rare-event searching is arguably the most natural application of grid computing, where computational tasks are distributed to a large collection of clients (which comprise the computation grid) in such a way that clients are rewarded for performing tasks assigned to them. Although natural, rare-event searching presents significant challenges for a computation supervisor, who partitions...
Digital signature systems provide a way to transfer trust from the public key to the signed data; this is used extensively within PKIs. However, some applications need a transfer of trust in the other direction, from the signed data to the public key. Such a transfer is cryptographically robust only if the signature scheme has a property which we name exclusive ownership. In this article, we show...
Recently, several public key exchange protocols based on symbolic computation in non-commutative (semi)groups were proposed as a more efficient alternative to well established protocols based on numeric computation. Notably, the protocols due to Anshel-Anshel-Goldfeld and Ko-Lee et al. exploited the conjugacy search problem in groups, which is a ramification of the discrete logarithm problem. However,...
Balanced Oil and Vinegar signature schemes and the unbalanced Oil and Vinegar signature schemes are public key signature schemes based on multivariable polynomials. In this paper, we suggest a new signature scheme, which is a generalization of the Oil-Vinegar construction to improve the efficiency of the unbalanced Oil and Vinegar signature scheme. The basic idea can be described as a construction...
We present Badger, a new fast and provably secure MAC based on universal hashing. In the construction, a modified tree hash that is more efficient than standard tree hashing is used and its security is proven. Furthermore, in order to derive the core hash function of the tree, we use a novel technique for reducing Δ-universal function families to universal families. The resulting MAC is very efficient...
Intrusion Detection Systems (IDSs) are widely deployed in computer networks to stand against a wide variety of attacks. IDSs deployment raises a serious problem, namely managing of a large number of triggered alerts. This problem becomes worse by the fact that some commercial IDSs may generate thousands of alerts per day. Identifying the real alarms from the huge volume of alarms is a frustrating...
We introduce novel techniques for organizing the indexing structures of how data is stored so that alterations from an original version can be detected and the changed values specifically identified. We give forensic constructions for several fundamental data structures, including arrays, linked lists, binary search trees, skip lists, and hash tables. Some of our constructions are based on a new reduced-randomness...
To make up for the incompleteness of the known behaviors of a computing resource, model generalization is utilized to infer more behaviors in the behavior model besides the known behaviors. In principle, model generalization can improve the detection rate but may also degrade the detection performance. Therefore, the relation between model generalization and detection performance is critical for intrusion...
We propose a new secure communication primitive called an Intrusion-Resilient Channel (IRC) that limits the damage resulting from key exposures and facilitates recovery. We define security against passive but mobile and highly adaptive adversaries capable of exposing even expired secrets. We describe an intuitive channel construction using (as a black box) existing public key cryptosystems. The simplicity...
Strong security notions often introduce strong constraints on the construction of cryptographic schemes: semantic security implies probabilistic encryption, while the resistance to existential forgeries requires redundancy in signature schemes. Some paddings have thus been designed in order to provide these minimal requirements to each of them, in order to achieve secure primitives. A few years...
Let us consider the following situation: (1) a client, who communicates with a variety of servers, remembers only one password and has insecure devices with very-restricted computing power and built-in memory capacity; (2) the counterpart servers have enormous computing power, but they are not perfectly secure; (3) neither PKI (Public Key Infrastructures) nor TRM (Tamper-Resistant Modules) is available...
This paper presents a first example of secure identity based encryption scheme (IBE) without redundancy in the sense of Phan and Pointcheval. This modification of the Boneh-Franklin IBE is an hybrid construction that is proved to be secure (using proof techniques borrowed from those for KEM-DEM constructions) in the random oracle model under a slightly stronger assumption than the original IBE and...
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