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Informally, an obfuscator O is an (efficient, probabilistic) "compiler" that takes as input a program (or circuit) P and produces a new program O(P) that has the same functionality as P yet is "unintelligible" in some sense. Obfuscators, if they exist, would have a wide variety of cryptographic and complexity-theoretic applications, ranging from software protection to homomorphic encryption to complexity-theoretic analogues of Rice's theorem. Most of these applications are based on an interpretation of the "unintelligibility" condition in obfuscation as meaning that O(P) is a "virtual black box," in the sense that anything one can efficiently compute given O(P), one could also efficiently compute given oracle access to P. In this work, we initiate a theoretical investigation of obfuscation. Our main result is that, even under very weak formalizations of the above intuition, obfuscation is impossible. We prove this by constructing a family of efficient programs P that are unobfuscatable in the sense that (a) given any efficient program P′ that computes the same function as a program P ∈ P, the "source code" P can be efficiently reconstructed, yet (b) given oracle access to a (randomly selected) program P ∈ P, no efficient algorithm can reconstruct P (or even distinguish a certain bit in the code from random) except with negligible probability. We extend our impossibility result in a number of ways, including even obfuscators that (a) are not necessarily computable in polynomial time, (b) only approximately preserve the functionality, and (c) only need to work for very restricted models of computation (TC[sup 0]).We also rule out several potential applications of obfuscators, by constructing "unobfuscatable" signature schemes, encryption schemes, and pseudorandom function families. Categories and Subject Descriptors: D.4.6 [Operating Systems]: Security and Protection -- Cryptographic Controls; F.1.3 [Computation by Abstract Devices]: Complexity Measures and Classes General Terms: Theory [ABSTRACT FROM AUTHOR]

Two-way communication has been identified as the smart grid flagship feature that enables the smart grid to attain its outcomes over the legacy power grid. Integrating communication networks into the power grid will motivate malicious attackers to target information exchange. Therefore, achieving secure and authentic communication in the smart grid networks is an indispensable requirement. In this paper, we propose a sophisticated hybrid encryption scheme that incorporates public and symmetric key encryptions to secure smart metering network. Elliptic Curve Integrated Encryption Scheme (ECIES) and Advanced Encryption Scheme (AES) are chosen as the building blocks for the proposed scheme. In order to optimize the computation overhead of ECIES, a precomputation procedure is presented to provide faster encryption/decryption. The proposed technique provides data integrity, confidentiality and authenticity as well as it resists against false data injection and message reply attacks. Simulation results show that the proposed approach surpasses some of the existing schemes in terms of computation, communication and storage overhead. [ABSTRACT FROM AUTHOR]

The article focuses on the study of the optical authentication system designed through lanthanide luminescence from physical unclonable functions (PUFs). Topics include the capacity of PUFs to prevent counterfeiting and encryption, the composition of the authentication system which include image analysis, hardware readers, and authentication software, and the importance of excitation-selected imaging of lanthanide ions doped in preventing the random patterns from being copied.

Random numbers play a vital role in cryptography, where they are used to generate keys, nonce, one-time pads, and initialization vectors for symmetric encryption. The quality of random number generator (RNG) has significant implications on vulnerability and performance of these algorithms. A pseudo-RNG uses a deterministic algorithm to produce numbers with a distribution very similar to uniform. True RNGs (TRNGs), on the other hand, use some natural phenomenon/process to generate random bits. They are nondeterministic, because the next number to be generated cannot be determined in advance. In this paper, a novel on-chip noise source, random telegraph noise (RTN), is exploited for simple and reliable TRNG. RTN, a microscopic process of stochastic trapping/detrapping of charges, is usually considered as a noise and mitigated in design. Through physical modeling and silicon measurement, we demonstrate that RTN is appropriate for TRNG, especially in highly scaled MOSFETs. Due to the slow speed of RTN, we purpose the system for on-chip seed generation for random number. Our contributions are: 1) physical model calibration of RTN with comprehensive 65- and 180-nm transistor measurements; 2) the scaling trend of RTN, validated with silicon data down to 28 nm; 3) design principles to achieve 50% signal probability by using intrinsic RTN physical properties, without traditional postprocessing algorithms, the generated sequence passes the National Institute of Standards and Technology (NIST) tests; and 4) solutions to manage realistic issues in practice, including multilevel RTN signal, robustness to voltage and temperature fluctuations and the operation speed. [ABSTRACT FROM PUBLISHER]

Cloud Computing is an transpiring trend in the modern world. It is a way of holding the Internet to use software or other IT services on demand. Due to its fast growth and popularity, number of users deposit their data and applications on the cloud. The impressive growth in cloud computing has proved to be promising innovation and more suitable for storing data and applications remotely. But its uses improvement is hindered by the security issue. Cloud doesn't provide more security for its services and storage purpose. The traditional security approach of encryption doesn't make cloud fully secure. So there is a need to develop such a technique which increases the security level of cloud. In order to solve the problem of data security in cloud computing system, lattice-based cryptographic schemes implements the so called "Fully Homomorphic Encryption (FHE) scheme", which allows processing directly on encrypted data and holds the promise eventually to solve the security problems with cloud computing. In this paper we survey on the existing lattice based FHE encryption techniques. Fully homomorphic encryption is a good solution to enhance security measures of cloud system that handles critical data. This makes cloud computing more stable and solid. [ABSTRACT FROM AUTHOR]

The articles in this special issue highlight recent advances along with the remaining challenges in the field of physical-layer communications security. [ABSTRACT FROM AUTHOR]

XML Encryption and XML Signature describe how to apply encryption and signing algorithms to XML documents. These specifications are implemented in a wide range of systems and frameworks processing sensitive data, including banking, eGovernment, eCommerce, military, and eHealth infrastructures. The article presents practical and highly critical attacks which allow to forge signed XML documents or reveal contents of encrypted XML data. [ABSTRACT FROM AUTHOR]

Although cryptographic software implementation is often performed by expert programmers, the range of performance and security driven options, as well as more mundane software engineering issues, still make it a challenge. The use of domain specific language and compiler techniques to assist in description and optimisation of cryptographic software is an interesting research challenge. In this paper we investigate two aspects of such techniques, focusing on Elliptic Curve Cryptography (ECC) in particular. Our constructive results show that a suitable language allows description of ECC based software in a manner close to the original mathematics; the corresponding compiler allows automatic production of an executable whose performance is competitive with that of a hand-optimised implementation. In contrast, we study the worrying potential for naïve compiler driven optimisation to render cryptographic software insecure. Both aspects of our work are set within the context of CACE, an ongoing EU funded project on this general topic. [ABSTRACT FROM AUTHOR]

The article discusses protocols for preventing attacks on password-based computer authentication. The use of passwords on insecure communication channels such as the Internet can allow others to eavesdrop and learn passwords. Challenge-response protocols have been established to protect passwords by requiring users to answer a challenge prior to password verification. A password-based encrypted key exchange uses session keys to prevent password attacks. A secure remote password (SRP) combines zero-knowledge proofs and asymmetric key-exchange protocols. Though the standard model of key exchange is utilized in cryptography, alternative models use block ciphers in place of ideal ciphers. Reverse Turing tests (RTT) prevent automated programs from stealing passwords.

This paper proposes an identity-based threshold decryption scheme IB-ThDec and reduces its security to the Bilinear Diffie–Hellman problem. Compared with previous work, this conceals two pairing computations in the ciphertext validity verification procedure. The formal proof of security of this scheme is provided in the random oracle model. Additionally, we show that IB-ThDec can be applied to the threshold key escrow and the mediated cryptosystems. [Copyright &y& Elsevier]

The proxy signature scheme enables an original signer to delegate his/her signing capability to a designated proxy signer, thereby the proxy signer can sign messages on behalf of the original signer. Recently, Zhou et al. Proposed two proxy-protected signature schemes. One is based on the RSA problem and the other is based on the integer factorization problem. In this paper, however, we point out that Zhou et al. ’s schemes are insecure against undelegated proxy signature attack because any user without the delegation of the original signer can generate a valid proxy signature. To solve this problem, an improved scheme is proposed and its security is analyzed. [Copyright &y& Elsevier]

In 1999, Solinas introduced families of moduli called the generalized Mersenne numbers (GMN5), which are expressed in low-weight polynomial form, p = f(t), where is limited to a power of 2. GMNs are very useful in elliptic curve cryptosystems over prime fields since modular reduction by a GMN requires only integer additions and subtractions. However, since there are not many GMNs and each GMN requires a dedicated implementation, GMNs are hardly useful for other cryptosystems. Here, we modify GMN by removing restriction on the choice oft. and restricting the coefficients of f(t) to 0 and ±1. We call such families of moduli low-weight polynomial form integers (LWPFIs). We show an efficient modular multiplication method using LWPFI moduli. LWPFI5 allow general implementation and there exist many LWPFI moduli. One may consider LWPFIs as a trade-oft between general integers and GMNs. [ABSTRACT FROM AUTHOR]

In this paper, we present a new technique to obtain biometric keys by using the fingerprint of a person for an optical image encryption system. The key generation scheme uses the fingerprint biometric information in terms of the amplitude mask (AM) and the phase mask (PM) of the reconstructed fingerprint image that is implemented using the digital holographic technique. Statistical tests have been conducted to check the randomness of the fingerprint PM key that enables its usage as an image encryption key. To explore the utility of the generated biometric keys, an optical image encryption system has been further demonstrated based on the phase retrieval algorithm and the double random phase encoding scheme in which keys for the encryption are used as the AM and the PM key. The advantage associated with the proposed scheme is that the biometric keys’ retrieval requires the simultaneous presence of the fingerprint hologram and the correct knowledge of the reconstruction parameters at the decryption stage, which not only verifies the authenticity of the person but also protects the valuable fingerprint biometric features of the keys. Numerical results are carried out to prove the feasibility and the effectiveness of the proposed encryption system. [ABSTRACT FROM AUTHOR]