Theses and Dissertations

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    Modeling and detecting attacks against key agreement protocols
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2012) Yadav, Anshu; Mathuria, Anish M.
    Key agreement protocols establish a shared secret key between two or more communicating parties willing to exchange data over insecure channels using symmetric key cryptography. Based on the number of members involved in the communication these protocols can be classied as a two party or group key agreement protocols. Various formal methods are available in the literature to analyze the security of such protocols. This helps in establishing the validity of any attacks, if found, or to prove the security of the protocols under given adversarial assumptions. In this thesis we analyze the security of several existing two party and group key agreement protocols. We used provable security models like eCK'08 and enhanced eCK and the DS model given as an algebraic approach by Delicata and Schneider to analyze a class of DH based key agreement protocols. The distinguishing feature of key agreement protocols from key transport protocols is that the former aims to ensure the contribution of all the honest participants so that no one can predetermine the key. In a poorly designed protocol, an insider adversary can control the key in different forms as dened by Pieprzyk and Wang. This type of attack is termed as key control. We also dene ephemeral key control w.r.t. dishonest insider where it is assumed that the adversary also knows the ephemeral secret of the victim honest participants. This assumption is based on several advanced attributes that assume ephemeral leakage. We analyze this attack on MTI protocols using DS model. We have shown weakness in some provably secure two party implicitly authenticated protocols and modeled the attacks in provable security model. We also analyzed key control in some group key agreement protocols. We have used the DS model to formally derive an attack shown by Pieprzyk on Burmester-Desmedt protocol and have also proposed attacks on static version of the group key agreement protocol proposed by Dutta and Barua.
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    Prolog based approach to reasoning about dynamic hierarchical key assignment schemes
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2011) Mundra, Anil Kumar; Mathuria, Anish M.
    The problem of allowing the higher level users access the information related to lower level is called Hierarchical Access Control Problem. In a hierarchical access control system, users are partitioned into a number of classes - called security classes, which are organized in a hierarchy. Hierarchies arise in systems where some users have higher privileges than others and a security class inherits the privileges of its descendant classes. A basic Hierarchical Key Assignment Scheme is a method of assigning an encryption key to each class in the hierarchy. In literature, there are number of such hierarchy schemes are available and many of them have formal proof models for security properties. Now a days mostly all the schemes have a solution for Dynamic Access Control problem. We found that for dynamic schemes no formal proof model is available so we can not make any arguments on security properties of such schemes. We present a new approach for automatic veri cation using Prolog for the analysis of existing dynamic and static hierarchical key assignment schemes and verify their security properties. We discover some new attacks on existing schemes and proposed a new scheme to overcome those attacks.
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    Collusion resistant fingerprinting
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2011) Juneja, Sandeep; Raval, Mehul S.
    Digital watermarking is used to carry information by embedding information into the cover data in a perceptually visible or non visible manner. In today's sea of digital information, there are many problems associated like identi cation of the owner of content, and detection of authorized content receivers. Digital ngerprinting, one of the application of watermarking, is one way to detect authorized content receivers from illegally redistributed media. One powerful scheme to broke digital ngerprint scenario is `collusion attack' in which users share information to remove their embed- ded ngerprint. In this research work, we have proposed a ngerprint technique that is robust against average collusion attack and has capability to trace colluders for images. Independent ngerprints are randomly generated using independent and identically distributed (IID) Gaussian source. We proposed two schemes. In rst scheme, n- gerprints were embedded using additive embedding rule and spread spectrum (SS) technique. This scheme is based on embedding ngerprint in di erent block of discrete cosine transformation (DCT). In second, ngerprints were embedded in independent components (ICs) generated by applying independent component analysis (ICA) on cover image. In both schemes, we used non-blind watermarking and correlation based detector. The result shows that the schemes are robust against average collusion at- tack.
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    Wireless LAN 802.11 security using elliptic curve cryptography
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2011) Singh, Saurabh; Das, Manik Lal
    IEEE 802.11 is a standard defines the specification of Wireless Local Area Network (WLAN), came into existence in 1997. As communication medium is wireless, security is a major concern to protect the data from adversary. Existing WLAN security is primarily based on Symmetric Key Cryptography (SKC). But, major disadvantage with SKC is establishment of secret key for secure data delivery. Public key cryptography(PKC) has many advantages over Symmetric key cryptography like key management key distribution over insecure channel etc. However, PKC requires a large key size in comparison to SKC to provide same level of security. This makes PKC costly operation and not suitable for the environment like WLAN where limited memory is available for WLAN devices. In recent years, Elliptic Curve Cryptography (ECC) has gained a lot of attention from research communities, because ECC seems to promise simillar or a better level of security with smaller key size in comparison with conventional PKC (e.g. RSA, DSS). These features make them workable under constraint environment. In this thesis, we have studied the security evolution of WLAN 802.11 with Wired Equivalent Privacy (WEP) and Wi-Fi Protected Access (WPA). We have observed some limitations of WEP and WPA. We, then, present a new protocol using ECC for mutual authentication and session key establishment. We compare our protocol with simillar protocols for wireless security and show that the proposed protocol is efficient w.r.t. space, bandwidth and computational cost at Client side. The security analysis of proposed protocol shows that it may achieve forward secrecy with respect to Client, joint key control, key integrity and resists guessing, replay, impersonantion attacks. A thorough forrmal security analysis is required to be done.
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    Efficient ASIC implementation of advanced encryption standard
    (Dhirubhai Ambani Institute of Information and Communication Technology, 2008) Joshi, Ashwini Kumar; Nagchoudhuri, Dipankar
    In spite of the many defense techniques, software vulnerabilities like buffer overflow, format string vulnerability and integer vulnerability is still exploited by attackers. These software vulnerabilities arise due to programming mistakes which allows security bugs to be exploited. Buffer overflow occurs when buffer is given more data than the capacity of it. Format string vulnerability arises when data supplied by attacker is passed to formatting functions as format string argument. Integer vulnerability occurs when program evaluates an integer to unexpected value due to integer overflows, underflows, truncation errors or signed conversion errors. The hardware based solution called tagged architecture protects a system against mentioned vulnerabilities. In tagged architecture, each memory byte is appended with one tag bit to mark data that comes from I/O. Whenever I/O supplied data is used to transfer control of a system or to access memory, an alert is raised and program is terminated. This thesis proposes a weakness of tagged architecture by finding false positives and false negatives on it. It also proposes the improvements to the tagged architecture to avoid found false positives on it. The prototype implementation of improved tagged architecture is done in SimpleScalar simulator. The SimpleScalar simulator is a architectural simulator. The security evaluation is done for tagged architecture and improved tagged architecture through benchmarks and synthetic vulnerable programs.